# US 4,394,514 A · Processes for preparing 4-substituted indoles

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- Number: US 4,394,514 A
- Document ID: US4394514A
- Status: Granted
- Kind: A
- Application number: 06/278,016
- Filed: 1981-06-29
- Granted: 1983-07-19
- Earliest claimed: 1981-04-30
- Assignees: SmithKline Beckman Corporation
- Inventors: Lawrence I. Kruse
- Web page: https://patentgrep.com/patent/US4394514A

## CPC

- C07D 209/08: with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, directly attached to carbon atoms of the hetero ring
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)

## Abstract

A new chemical sequence for preparing indoles is disclosed whose key reactions are reaction of a o-nitrotoluene with tris(dimethylamino)methane to give a .beta.-dimethylamino-o-nitrostyrene which is converted into a semicarbazone and cyclized.

## Claims

### Claim 1

The method of preparing a 4-substituted indole of the following formula: ##STR2## in which R is lower alkoxy, lower alkyl, benzyloxy or carbalkoxy, said alkoxy or alkyl groups being of 1-6 carbons, comprising the steps of;
(A) reacting a o-nitro-.beta.-dimethylaminostyrene of the formula: ##STR3## in which R is as defined above, with semicarbazide or an acid addition salt thereof at ambient temperature in aqueous dimethylformamide or dimethylacetamide until the reaction is substantially complete to give a semicarbazone of the formula ##STR4## in which R is as defined above, and (B) reacting said semicarbazone under standard low pressure catalytic hydrogenation conditions over a noble metal hydrogenation catalyst until the reaction is complete to give the desired 4-substituted indole.

### Claim 2 (depends on 1)

The method of claim 1 in which R is methoxy.

### Claim 3 (depends on 1)

The method of claim 1 in which R is benzyloxy.

### Claim 4 (depends on 1)

The method of claim 1 in which R is carbomethoxy.

### Claim 5 (depends on 1)

The method of claim 1 in which the catalyst is palladium-on-charcoal.