Tetrahydroindeno[1,2-D][1,3,2]oxazaboroles and their use as enantioselective catalysts
AssigneeSepracor Inc.
InventorsYun Gao, Yaping Hong, Charles M. Zepp
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Abstract
A method for the enantioselective reduction of prochiral ketones using catalytic amounts of tetrahydroindeno[1,2-d][1,3,2] oxazaboroles of formula II is disclosed. ##STR1## The oxazaboroles can be generated in situ from the corresponding cis-1-amino-2-indanols or imino indanols (III) ##STR2## Novel compounds of formulas II and III are also disclosed.
Claims11
A method for the enantiospecific reduction of a prochiral ketone to the corresponding alcohol comprising reacting said prochiral ketone with a borane reducing agent in an inert solvent in the presence of a catalytic amount which is a substoichiometric amount sufficient to effect the enantioselective conversion of said ketone to said alcohol, of a compound chosen from the group consisting of ##STR18## wherein R.sup.1 is hydrogen, alkyl, arylmethylene or heteroarylmethylene;
- heteroaryl is a 5- or 6-membered aromatic heterocyclic group containing up to three heteroatoms independently selected from the group consisting of N, O and S;
- R.sup.2 is;
- alkyl, benzyl, phenyl or substituted phenyl;
- and
- R.sup.4 is hydrogen, alkyl, aryl, halo, nitro or alkoxy.
A process for the enantioselective reduction of a prochiral ketone comprising
- (a) combining at least one equivalent of a borane reducing agent with a compound of formula ##STR20## wherein R.sup.3 is alkyl, aryl or a 5- or 6membered aromatic heterocyclic group containing up to three heteroatoms independently selected from the group consisting of N, O and S and R.sup.4 is hydrogen, alkyl, aryl, halo or alkoxy, in an inert solvent to provide a catalyst mixture;
- and
- (b) adding more than one equivalent of a prochiral ketone and a corresponding amount of a borane reducing agent to said catalyst mixture.
Dependencies are inferred from the claim text.