# US 10,000,500 B2 · Coelenterazine analogues

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- Number: US 10,000,500 B2
- Document ID: US10000500B2
- Status: Granted
- Kind: B2
- Application number: 15/661,582
- Filed: 2017-07-27
- Published: 2018-02-01
- Granted: 2018-06-19
- Earliest claimed: 2016-07-28
- Assignees: Promega Corporation
- Applicants: Promega Corporation
- Inventors: Mary Hall; Thomas Kirkland; Thomas Machleidt; Anton Shakhmin; Joel R. Walker
- Web page: https://patentgrep.com/patent/US10000500B2

## CPC

- C07D 487/04: Ortho-condensed systems
- A61K 49/0021: {the fluorescent group being a small organic molecule}
- C07D 519/00: Heterocyclic compounds containing more than one system of two or more relevant hetero rings condensed among themselves or condensed with a common carbocyclic ring system not provided for in groups C07D453/00 or C07D455/00
- C09K 11/06: containing organic luminescent materials
- C12Q 1/66: involving luciferase
- C12Y 113/12005: Renilla-luciferin 2-monooxygenase (1.13.12.5), i.e. renilla-luciferase
- C12Y 113/12013: Oplophorus-luciferin 2-monooxygenase (1.13.12.13)
- C09K 2211/1011: Condensed systems
- C09K 2211/1018: Heterocyclic compounds
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)
- A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C12Q: MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS (immunoassay G01N33/53); COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
- C12Y: ENZYMES

## Abstract

Described are coelenterazine analogs, methods for making the analogs, kits comprising the analogs, and methods of using the compounds for the detection of luminescence in luciferase-based assays.

## Claims

### Claim 1

A compound of formula (I)
or a tautomer, or a salt thereof, wherein
R5 is hydrogen, halogen, hydroxy, cyano, nitro, amino, alkylamino, dialkylamino, alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl;
R6 is alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl; or
R5 and R6 together with the atoms to which they are attached, form a 5- or 6-membered partially unsaturated or fully unsaturated ring, the 5- or 6-membered ring optionally containing 1, 2 or 3 heteratoms or heteroatom groups each independently selected from the group consisting of O, N, S, NO, SO and SO2 as ring members, the 5- or 6-membered ring optionally fused to an aryl, heteroaryl, heterocycle, or cycloalkyl, the 5- or 6-membered ring substituted with 0, 1, 2, 3, or 4 substituents, each independently selected from the group consisting of halogen, ═O, ═S, cyano, nitro, fluoroalkyl, alkoxyfluoroalkyl, fluoroalkoxy, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, alkylene, aryloxy, phenoxy, benzyloxy, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl; and
R8 is alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl;
wherein said alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, and cycloalkenyl, at each occurrence, are independently substituted with 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 substituents, each independently selected from the group consisting of halogen, ═O, ═S, cyano, nitro, fluoroalkyl, alkoxyfluoroalkyl, fluoroalkoxy, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, alkylene, aryloxy, phenoxy, benzyloxy, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl;
provided that the following compounds are excluded from formula (I):
8-benzyl-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one; and
8-benzyl-2-(furan-2-ylmethyl)-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one.

### Claim 2 (depends on 1)

The compound of claim 1, wherein R5 is hydrogen, cyano, C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, or phenyl.

### Claim 3 (depends on 1)

The compound of claim 1, wherein R6 is aryl, bicyclic aryl, tricyclic aryl, biphenyl, heteroaryl, bicyclic heteroaryl, or tricyclic heteroaryl; substituted with 0, 1, 2, or 3 substituents, each independently selected from the group consisting of halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, and C1-C6-dialkylamino.

### Claim 4 (depends on 1)

The compound of claim 1, wherein R6 is
wherein
X1-X43 are each independently CR11 or N, wherein R11, at each occurrence, is independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; provided that one of X6-X13 is C where the R6 attaches to the parent molecular formula; provided that one of X14-X23 is C where the R6 attaches to the parent molecular formula; provided that one of X24-X33 is C where the R6 attaches to the parent molecular formula; provided that one of X34-X38 is C to attach to the ring containing X39-X43;
Y1, Y5, Y15, and Y22 are O, S, or NR12, wherein R12 is hydrogen, C1-C6-alkyl, or C1-C6-haloalkyl;
Y30 is N;
Y2-Y4, Y6-Y4, Y6-Y21, and Y23-Y29 are each independently CR13 or N, wherein R1, at each occurrence, is independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; provided that one of Y9-Y14 is C where the R6 attaches to the parent molecular formula; provided that one of Y16-Y21 is C where the R6 attaches to the parent molecular formula; and provided that one of Y23-Y29 is C where the R6 attaches to the parent molecular formula.

### Claim 5 (depends on 1)

The compound of claim 1, wherein R6 is selected from the group consisting of:

### Claim 6 (depends on 1)

The compound of claim 1, wherein R5 and R6 together with the atoms to which they are attached, form a 6-membered partially unsaturated or fully unsaturated ring, the 6-membered ring optionally containing 1, 2 or 3 heteratoms or heteroatom groups each independently selected from the group consisting of O, N, S, NO, SO and SO2 as ring members, the 6-membered ring optionally fused to an aryl, 5- or 6-membered heteroaryl, 5- or 6-membered heterocycle, or 5-, 6- or 7-membered cycloalkyl, the 6-membered ring and the optionally fused ring each independently substituted with 0, 1, 2, 3, or 4 substituents each independently selected from the group consisting of halogen, ═O, ═S, cyano, nitro, fluoroalkyl, alkoxyfluoroalkyl, fluoroalkoxy, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, alkylene, aryloxy, phenoxy, benzyloxy, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl.

### Claim 7 (depends on 1)

The compound of claim 1, wherein R5 and R6 together with the atoms to which they are attached, form a ring system selected from the group consisting of:
wherein
Z1-Z10 and Z13-Z16 are each independently CR14 or N, wherein R14, at each occurrence, is independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; and
Z11 and Z12 are each independently CR15R16, NR17, O, or S; wherein R15 and R16, at each occurrence, are each independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; and R17, at each occurrence, is independently selected from the group consisting of hydrogen, C1-C6-alkyl, and C1-C6-haloalkyl.

### Claim 8 (depends on 1)

The compound of claim 1, wherein R5 and R6 together with the atoms to which they are attached, form a ring system selected from the group consisting of:

### Claim 9 (depends on 1)

The compound of claim 1, wherein R8 is aryl, bicyclic aryl, tricyclic aryl, biphenyl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, or cycloalkyl; substituted with 0, 1, 2, or 3 substituents, each independently selected from the group consisting of halogen, ═O, ═S, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, and C1-C6-dialkylamino.

### Claim 10 (depends on 1)

The compound of claim 1, wherein R8 is
wherein
E1-E43 are each independently CR21 or N, wherein R21, at each occurrence, is independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; provided that one of E6-E13 is C where the R8 attaches to the parent molecular formula; provided that one of E4-E23 is C where the R8 attaches to the parent molecular formula; provided that one of E24-E33 is C where the R8 attaches to the parent molecular formula; provided that one of E34-E38 is C to attach to the ring containing E39-E43;
J1, J5, J15, and J22 are O, S, or NR22, wherein R22 is hydrogen, C1-C6-alkyl, or C1-C6-haloalkyl;
J30 is N;
J2-J4, J6-J14, J16-J21, and J23-J29 are each independently CR23 or N, wherein R23, at each occurrence, is independently selected from the group consisting of hydrogen, halogen, hydroxy, cyano, amino, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-haloalkyl, C1-C6-haloalkoxy, C1-C6-alkylamino, C1-C6-dialkylamino, and C1-C6-heteroalkyl; provided that one of J9-J14 is C where the R8 attaches to the parent molecular formula; provided that one of J6-J21 is C where the R8 attaches to the parent molecular formula; and provided that one of J23-J29 is C where the R8 attaches to the parent molecular formula.

### Claim 11 (depends on 1)

The compound of claim 1, wherein R8 is selected from the group consisting of:

### Claim 12 (depends on 1)

The compound of claim 1, having formula (I-a), (I-b), (I-c), (I-d), or (I-e),
(I-e);
wherein each indicates an optional bond.

### Claim 13

A compound selected from the group consisting of:
8-benzyl-2-(furan-2-ylmethyl)-6-(naphthalen-1-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(naphthalen-2-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
6-(anthracen-9-yl)-8-benzyl-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(phenanthren-9-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
6-([1,1′-biphenyl]-4-yl)-8-benzyl-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(2-methoxypyrimidin-5-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
4-(8-benzyl-2-(furan-2-ylmethyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-6-yl)benzonitrile;
8-benzyl-2-(furan-2-ylmethyl)-6-(quinolin-6-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(4-methoxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(3-methoxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(2-methoxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-6-(4-fluorophenyl)-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-benzyl-2-(furan-2-ylmethyl)-6-(3-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
6-(2-aminophenyl)-8-benzyl-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
6-(3-aminophenyl)-8-benzyl-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one; and
6-(4-aminophenyl)-8-benzyl-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-methyl)-6,8-diphenlimidazo[1,2-a]pyrazin-3(7H)-one:
8-cyclopentyl-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(naphthalen-1-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one:
2-(furan-2-ylmethyl)-8-(naphthalen-2-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-([1,1′-biphenyl]-4-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(phenanthren-9-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(phenylethynyl)imidazo[1,2-a]pyrazin-3(7H)-one:
(E)-2-(furan-2-ylmethyl)-6-phenyl-8-styrylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(benzofuran-2-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one:
8-(benzo[b]thiophen-2-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(benzo[c][1,2,5]oxadiazol-5-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(imidazo[1,2-a]pyridin-6-yl)-6-phenylimidazo[1,2-a]pyrazin-3-(7H)-one;
2-(furan-2-ylmethyl)-8-(1H-indol-5-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(benzo[d]thiazol-5-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(2-methyl-2H-indazol-6yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
5-(2-(furan-2-ylmethyl)-3-oxo-6phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)-1,3-dimethylpyrimidine-2,4(1H,3H)-dione;
2-(furan-2-ylmethyl)-8-(1-methyl-2-oxo-1,2-dihydropyridin-3-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(1-methyl-6-oxo-1,6-dihydropyridin-3-yl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl-6-phenyl-8-(3,4,5-trifluorophenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-(4-fluorophenyl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-8-(4-nitrophenyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
4-(2-(furan-2-ylmethyl)-3-oxo-6-phenyl-3,7-dihydroimidazo-[1,2-a]pyrazin-8-yl)benzonitrile;
3-(2-(furan-2-ylmethyl)-3-oxo-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)benzonitrile;
8-(4-(dimethylamino)phenyl)-2-(furan-2-ylmethyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(thiophen-3-yl)imidazo[1,2-a]pyrazin-3(7H-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(thiophen-2-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
5-(2-(furan-2-ylmethy)-3-oxo-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-8 yl)thiophene-2-carbonitile;
8-(5-chlorothiophen-2-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2a]pyrazin-3(7H)-one;
8-(3-chlorothiophen-2-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2ylmethyl)-6-phenyl-8-(pyridin-3-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-(6-fluoropyridin-3-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(2-fluoropyridin-3-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(2-chloropyridin-3-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(pyridin-4-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-(2-fluoropyridin-4 yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
8-(2-chloropyridin-4-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(quinolin-4-yl)imidazol[1,2-a]pyrazin-3(7H)-one;
8-(2,6-dichloropyridin-4-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(2-(trifluoromethyl)pyridin-4-yl)imidazol[1,2-a]pyrazin-3(7H)-one;
8-(2-bromopyridin-4-yl)-2-(furan-2-ylmethyl)-6-phenylimidazo[1,2-a]pyrazin-3 (7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(thiazol-5-yl)imidazol[1,2-a]pyrazin-3(7H)-one; and
5-(2-(furan-2-ylmethyl)-3-oxo-6 phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)-1-methyl-1H-pyrrole-2-carbonitrile;
6,8-difuran-2-yl)-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6,8-di(thiophen-2-yl)imidazo[1,2a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-(1-methyl-1H-pyrazol-3-yl)-8-(1-methyl-1H-pyrazol-4-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
8-(2-fluoropyridin-4-yl)-2-(furan-2-ylmethyl)-6-(thiophen-2-yl)imidazo[1,2-a]pyrazin-3(7H)-one;
5-(2-(furan-2-ylmethyl)-3-oxo-6-(thiophen-2-yl)-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)thiophene-2-carbonitrile;
26,8-bis(2-fluoropyridin-4-yl)-2-(furan-2-ylmethyl)imidazol[1,2-a]pyrazin-3(7H)-one;
2-(furan-2-ylmethyl)-6-phenyl-8-(phenylethynyl)imidazo[1,2-a]pyrazin-3(7H)-one;
6-(4-aminophenyl)-2-(furan-2-ylmethyl)-8(quinolin-4-yl)imidazol[1,2-a]pyrazin-3(7H)-one;
5-(6-(4-aminophenyl)-2-(furan-2-ylmethyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)thiophene-2-carbonitile;
6,8-bis(4-aminophenyl)-2-(furan-2-ylmethyl)imidazo[1,2-a]pyrazin-3(7H)-one,
2-(furan-2-ylmethyl)-6-(4-hydroxyphenyl)-8-(quinolin-4-yl)imidazo[1,2-a]pyrazin-3(7H)-one; and
5-(2-furan-2-ylmethyl)-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-8-yl)thiophene-2-carbonitrile;
2-(furan-2-ylmethyl)-5,6,8-triphenylimidazo[1,2-a]pyrazin-3(7H)-one; and
2-(furan-2-ylmethyl)-3-oxo-6,8-diphenyl-3,7-dihydroimidazo[1,2-a]pyrazine-5-carbonitrile;
4-(2-chloropyridin-4-yl)-2-(furan-2-ylmethyl)imidazo[1,2-a]quinoxalin-1(5H)-one;
5-(2-(furan-2-ylmethyl)-1-oxo-1,5-dihydroimidazo[1,2-a]quinoxalin-4-yl)thiophene-2-carbonitrile;
12-(2-chloropyridin-4-yl)-2-(furan-2-ylmethyl)-5,11-dihydrobenzo[f]imidazo[1,2-a]quinoxalin-3(6H)-one;
5-(2-(furan-2-ylmethyl)-3-oxo-3,5,6,11-tetrahydrobenzo[f]imidazo[1,2-a]quinoxalin-12-yl)thiophene-2-carbonitrile; and
2-(furan-2-ylmethyl)-12-(quinolin-4-yl)-5,11-dihydrobenzo[f′]imidazo[1,2-a]quinoxalin-3(6H)-one;
8-(2-chloropyridin-4 yl)-2-(furan-2-ylmethyl)-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;
12-(2-chloropyridin-4-yl)-2-(furan-2-ylmethyl)benzo[f]imidazo[1,2-a]quinoxalin-3(11H)-one,
5-(2-(furan-2-ylmethyl)-3-oxo-3,11-dihydrobenzo[f]imidazo[1,2-a]quinoxalin-12-yl)thiophene-2-carbonitile; and
2-(furan-2-ylmethyl)-12-(quinolin-4-yl)benzo[f′]imidazo[1,2-a]quinoxalin-3(11H)-one;
2-benzyl-5-ethynyl-6,8-diphenylimidazo[1,2-a]pyrazin-3(7H)-one;
2-benzyl-3-oxo-6,8-diphenyl-3,7-dihydroimidazo[1,2-a]pyrazine-5-carbonitrile
2-benzyl-5-(dimethylamino)-6,8-diphenylimidazo[1,2-a]pyrazin-3(7H)-one; and
2-benzyl-5-methoxy-6,8-diphenylimidazo[1,2-a]pyrazin-3(7H)-one;
or a tautomer, or a salt thereof.

### Claim 14

A compound of formula (II),
or a tautomer, or a salt thereof, wherein
Rx is halogen, hydroxy, cyano, nitro, amino, alkylamino, dialkylamino, alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl;
p is 0, 1, 2, 3, 4, or 5;
R5a is hydrogen, halogen, hydroxy, cyano, nitro, amino, alkylamino, dialkylamino, alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl;
R6a is alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl; or
R5a and R6a together with the atoms to which they are attached, form a 5- or 6-membered partially unsaturated or fully unsaturated ring, the 5- or 6-membered ring optionally containing 1, 2 or 3 heteratoms or heteroatom groups each independently selected from the group consisting of O, N, S, NO, SO and SO2 as ring members, the 5- or 6-membered ring optionally fused to an aryl, heteroaryl, heterocycle, or cycloalkyl, the 5- or 6-membered ring substituted with 0, 1, 2, 3, or 4 substituents, each independently selected from the group consisting of halogen, ═O, ═S, cyano, nitro, fluoroalkyl, alkoxyfluoroalkyl, fluoroalkoxy, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, alkylene, aryloxy, phenoxy, benzyloxy, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl; and
R8a is alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, or cycloalkenyl;
wherein said alkyl, alkenyl, alkynyl, alkoxy, heteroalkyl, aryl, bicyclic aryl, tricyclic aryl, heteroaryl, bicyclic heteroaryl, tricyclic heteroaryl, heterocycle, cycloalkyl, and cycloalkenyl, at each occurrence, are independently substituted with 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 substituents, each independently selected from the group consisting of halogen, ═O, ═S, cyano, nitro, fluoroalkyl, alkoxyfluoroalkyl, fluoroalkoxy, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, alkylene, aryloxy, phenoxy, benzyloxy, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl;
provided that Rx is not 4-hydroxy when p is 1, R5a is not hydrogen, or R8a is not benzyl, or any combination thereof.

### Claim 15 (depends on 1)

A kit comprising a compound of claim 1.

### Claim 16 (depends on 1)

A method for detecting luminescence in a sample, the method comprising
contacting a sample with a compound of claim 1;
contacting the sample with a coelenterazine-utilizing luciferase, if it is not present in the sample; and
detecting luminescence.

### Claim 17 (depends on 1)

A method for detecting luminescence in a transgenic animal comprising
administering a compound of claim 1 to a transgenic animal; and detecting luminescence;
wherein the transgenic animal expresses a coelenterazine-utilizing luciferase.

### Claim 18 (depends on 14)

A kit comprising a compound of claim 14.

### Claim 19 (depends on 14)

A method for detecting luminescence in a sample, the method comprising contacting a sample with a compound of claim 14;
contacting the sample with a coelenterazine-utilizing luciferase, if it is not present in the sample; and
detecting luminescence.

### Claim 20 (depends on 14)

A method for detecting luminescence in a transgenic animal comprising administering a compound of claim 14 to a transgenic animal; and
detecting luminescence;
wherein the transgenic animal expresses a coelenterazine-utilizing luciferase.