Instant-Ylid: ein lagerfähiges und gebrauchsfertiges Wittig-Reagenz

Mixts. prepd. from alkyltriphenylphosphonium bromides and powd. NaNH2 were stored indefinitely. Upon addn. of an ethereal solid, however, they immediately generated the ylide, which then reacted with aldehydes, ketones, and formates. The use of such instant ylide mixts. offered distinct advantages over conventional Wittig procedures: optimum yields (even with enolizable ketones), highest cis/trans ratios, largest range of applicability, shortest reaction times, and easiest handling. Thus, condensation of Ph3:CHEt with BzH gave 94% (Z)-PhCH:CHEt and 6% (E)-PhCH:CHEt. Among the approx. 30 compds. prepd. were cis- and trans-stilbenes, methylenecyclohexane, and cis- and trans-BuOCH:CHEt. [on SciFinder (R)]