Process for preparing intermediates useful in the synthesis of vitamin D compounds
AssigneeHoffmann-La Roche Inc.
InventorAndrzej Robert Daniewski
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Abstract
The invention relates to an improved process for preparing [(3aR,4S,7aS)4-bromooctahydro-7a-methyl-1H-indene-1,5-dione]. (S)-(+)-2,3,7,7a-tetrahydro-7a-methyl-1H-indene-1,5(6H)-dione is reduced by reaction with diisobutylaluminum hydride and hexamethylphosphoric triaminde in the presence of a catalyst of the formula R—Cu, wherein R is and R1, R2 and R3 are each, independently, selected from the group consisting of C1-7 alkyl, phenyl, phenyl substituted by at least one C1-4 alkyl group, benzyl, or benzyl substituted by at at least one C1-4 alkyl group to form a reductate. The reductate is then treated with a bromine-containing electrophile to yield (3aR,4S,7aS)4-bromooctahydro-7a-methyl-1H-indene-1,5-dione.
Claims7
A process for preparing (3aR,4S,7aS)-4-bromooctahydro-7a-methyl-1H-indene-1,5-dione, which comprises:
- (a) reducing (S)-(+)-2,3,7,7a-tetrahydro-7a-methyl-1 H-indene-1,5(6H)-dione by reacting it with diisobutylaluminum hydride and hexamethylphosphoric triaminde in the presence of a catalyst of the formula R—Cu, wherein R is
- and R1, R2 and R3 are each, independently, selected from the group consisting of C1-7 alkyl, phenyl, phenyl substituted by at least one C1-4 alkyl group, benzyl, or benzyl substituted by at least one C1-4 alkyl group to form a reductate;
- and
- (b) treating the reductate with a bromine-containing electrophile to yield (3aR,4S,7aS)-4-bromooctahydro-7a-methyl-1H-indene-1,5-dione.
Dependencies are inferred from the claim text.