STEREOCHEMISTRY OF DIRECT OLEFIN FORMATION FROM CARBONYL-COMPOUNDS AND LITHIATED HETEROCYCLIC SULFONES

The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series. The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems. From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained : (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or alpha,beta-ethylenic or aromatic aldehydes. (Z)-olefins arise : (i) from propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes. Possible mechanisms for this new olefination procedure were examined.