Syntheses of N-heterocyclic carbenes and intermediates therefor
AssigneeUmicore AG & Co. KG
InventorsSteven P. Nolan, Sebastien Meiries
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Abstract
A method of preparing a 2,6 disubstituted anilines includes, reacting a 2-amino isophthalic acid diester with sufficient Grignard reagent R2CH2MgX to form the corresponding diol product, dehydrating the diol product to the corresponding dialkene; and hydrogenating the diol product to form the corresponding aniline. The 2,6 disubstituted anilines can be used to produce N-Heterocyclic Carbenes (NHCs). The NHCs can find application in various fields such as organic synthesis, catalysis and macromolecular chemistry. Palladium catalysts containing the NHCs are also described.
Claims4
An imidazolium salt of structure III;
- wherein X− is a halogen anion, each R2 is the same and is n-propyl;
- and wherein the groups Z1 and Z3 are H and the group Z2 is selected from methyl, methoxy and —NMe2.
A metal complex comprising an N-heterocyclic carbene prepared from an imidazolium salt of structure XX;
- wherein X− is a halogen anion, each R2 is the same and selected from ethyl and n-propyl;
- and Z1, Z2, and Z3 is a substituent independently selected from the group consisting of —H, —I, —CF3, —OR5, —R6 and —NR72;
- wherein each group R5,R6 or R7 is independently selected from the group consisting of:
- alkyl that may be unsaturated, substituted alkyl that may be unsaturated, aryl, substituted aryl, aralkyl and substituted aralkyl;
- or from an imidazolium salt of structure XVII or XXa:
- wherein X− is an anion, the groups R2 are the same and selected from H, methyl, ethyl, n-propyl and
- wherein either R3 is H and R4 is alkyl that may be substituted, or
- each of R3, R4 are an independently selected alkyl that may be substituted;
- and
- Z1, Z2, Z3 are independently selected from the group consisting of:
- —H, —I, —CF3, —OR5, —R6 and —NR72;
- wherein each group R5, R6 or R7 is independently selected from the group consisting of:
- alkyl that may be unsaturated, substituted alkyl that may be unsaturated, aryl, substituted aryl, aralkyl and substituted aralkyl.
A method of preparing an N-heterocyclic carbene, the method comprising:
- reacting an aniline of general formula I:
- wherein each group R2 is n-propyl;
- and
- wherein the groups Z1, Z2 and Z3 are H;
- with glyoxal to form a diimine of general formula II;
- cyclizing the diimine of structure II with paraformaldehyde to form an imidazolium salt of structure Ill;
- wherein X− is an anion;
- and
- reacting the imidazolium salt of structure Ill with a base to form the N-heterocyclic carbene.
Dependencies are inferred from the claim text.