ENANTIOSELECTIVE SYNTHESIS OF CIS-2(S)AMINO-1-D-INDANE AND TRANS-2(S)AMINO-1-D-INDANE - DEBROMINATIVE [1,2]-HYDRIDE SHIFT REARRANGEMENT BY REDUCTION OF CIS-2-AZIDO-1-BROMOINDANE WITH LIALD4

This article describes the synthesis of the racemic and optically pure forms of (1R,2S)-cis- and (1S,2S)-trans-2-Amino-1-d-indanes 2 {94% ee } and 3 {83% ee} (ee determined by H-2 NMR in chiral liquid crystal PB LG/CH2Cl2, Courtieu, J. et al. J. Am. Chem. Soc. 1995, 117, 6520) prep ared by LiAlD4 reduction of (+/-)- and (1S,2S)-trans-2-azido-1-bromomo indane (11) {87% ee} and (+/-) and (1R,2S)-cis-2-azido-1-[(methanesulf onyl)oxy]indane (10) {83% ee}, respectively. Whereas the LiAlD4 reduct ion of trans-2-azido-1-bromomoindane (11) led to cis-2-amino-1-d-indan e 2 by a S(N)2 pathway, exclusively, the reduction of cis-1-bromo deri vative 12 gave only small amounts of the S(N)2 product trans-2-amino-1 -d-indane (3) (15%) accompanied by 2-amino-2-d-indane (4) (85%) in whi ch the deuterium atom is incorporated in alpha position to the amino g roup. It was established that the primary amine 4 comes from a stereos pecific [1,2]-hydride shift rearrangement, We propose that the azido g roup is reduced first, and the [1,2]-hydride shift rearrangement preva ils over the competitive S(N)2 substitution. The exclusive formation o f trans-2-amino-1-d-indane (3) requires cis-2-azido-1-[(methanesulfony l)oxy]indane (10) where the mesylate assisted by electrophilic Li+ cat ion switches the deuteride attack to the ester carbon and the direct S (N)2 substitution occurs before the azide is reduced.