Chiral carbanions, III - Configurational stability and stannylation of dipole-stabilised cyclic tertiary benzylic alpha-oxycarbanions, which occurs with retention or inversion configuration depending on R and X of R3SnX used

2,4,6-Triisopropylbenzoates of 1-indanol and 1-tetralol tee 98%) are deprot onated at -78 degrees C in hexane by sBuLi/TMEDA to give partly configurati onally labile organolithium intermediates 5a and 5b, which are deuterated b y MeOD with retention of configuration. These intermediates are stannylated by trimethyltin chloride with inversion as determined by lithiodestannylat ion followed by addition of MeOD to produce deuterated esters of low ee. St annylation of (S)-5b with (-)-menthyldimethyltin bromide affords stannane 7 (de greater than or equal to 95%) with inversion. The carbanion derived fr om (S)-1-indanyl N,N-diisopropylcarbamate (9) is configurationally stable. It reacts with trimethyltin chloride favouring inversion of configuration ( ee up to 17%). Tributyltin chloride and tributyltin triflate yield stannane s 11b of opposite stereochemistry, the latter giving retention of configura tion. Tributyltin bromide behaves similarly to the chloride, but the ee of the reaction product is only about 30%.