Enantiospecific preparation of [(2 r,6 s)- endo]-5-aza-1,10,10-trimethyl-3-oxatricyclo[5.2.1.0 2,6]decan-4-one by a nitrene-mediated route from [(1 s)- endo]-(−)-borneol and its utility as a chiral auxiliary in some asymmetric transformations

Abstract

Attempted chiral aziridination of styrene by addition of optically-active alkoxycarbonylnitrene 5 derived from [(1 s)- endo]-(−)-bornyl- p-nitrobenzenesulphonoxycarbonate 4 is reported. No measurable asymmetric induction is observed under the various conditions employed, but in the absence of alkene, a tricyclic oxazolidin-2-one 8 is formed to which preparatively simpler access can be gained by thermal decomposition of azidoformate 7, either in 1,1,2,2-tetrachloroethane (50%) or by spray pyrolysis (58%). The oxazolidin-2-one 8 is demonstrated to be a successful chiral auxiliary by contemporary standards in a variety of asymmetric transformations, including alkylation, acylation, and aldol reactions for which high levels of asymmetric induction are observed. Diethylaluminium chloride-catalysed Diels-Alder reactions exhibit poorer selectivity except for the cinnamoyl derivative 23 which is stereospecific.