Alkene Synthesis Using Phosphonium Ylides as Umpolung Reagents

Abstract

We report a transformation between a wellknown nucleophile, phosphonium ylide, and an electrophile. Subsequent ylide-ylide coupling achieves unusual (Z)selectivity as compared to the conventional Wittig olefination. The synthesis of medium-sized ring olefins has also been demonstrated, together with a one-pot olefination from activated halides.

Aerobic Oxidative Dehydrogenation of Ketones to 1,4-Enediones

“…In addition, by virtue of their distinctive electrophilicity and electron affinity, they have been used as highly reactive electrophiles and dienophiles to construct complex molecules . Owing to their importance, the synthetic methodologies of 1,4-enediones have attached considerable attention, and remarkable progress has been made over the past decades. − Traditionally, 1,4-enediones were synthesized by oxidative ring opening of furan and thiophene derivatives, decomposition of α-diazo carbonyl compounds, and Wittig reaction . In 2003, Yu and Corey developed an oxidative protocol to synthesize 1,4-enediones from α,β -enones utilizing a Pd­(OH) 2 -on-C/K 2 CO 3 / t -BuOOH system (Scheme a) .…”