ANION REACTIONS OF 1,3-DITHIANE 1,3-DIOXIDE WITH CARBONYL-COMPOUNDS -HIGH DIASTEREOSELECTIVITY WITH AROMATIC-ALDEHYDES UNDER CONDITIONS OFEQUILIBRIUM CONTROL
Vk. Aggarwal et al., ANION REACTIONS OF 1,3-DITHIANE 1,3-DIOXIDE WITH CARBONYL-COMPOUNDS -HIGH DIASTEREOSELECTIVITY WITH AROMATIC-ALDEHYDES UNDER CONDITIONS OFEQUILIBRIUM CONTROL, Journal of organic chemistry, 60(7), 1995, pp. 2174-2182
We have investigated the anion chemistry of trans-1,3-dithiane 1,3-dio
xide (4) with aldehydes and ketones, and we have found that this reage
nt undergoes highly selective addition reactions with aromatic aldehyd
es but only when reactions are under equilibrium control (achieved usi
ng Na anion of 4). Other metals invetsigated (Li, Mg, Al, Ce, Ti) gave
either poorer selectivity or caused decomposition of 4. Zn-4 did give
improved selectivity at low temperature but only with aromatic aldehy
des. Reactions with ketones were limited to those without a-branching.
A model that accounts for the high diastereoselectivity observed with
aromatic aldehydes is presented.