Elongated phosphoranes by C–C coupling of haloaroylmethylidenetriphenylphosphoranes: synthesis and applications

Abstract

Haloaroylmethylidenephosphoranes 3 can be subjected to Pd(0) mediated C–C coupling reactions to yield diaryl-, arylhetaryl-, dihetaryl, arylethenylaryl/hetaryl- and arylethynylaryl/hetaryl-carbonylmethylidenephosphoranes 4–9. Suzuki–Kumada reactions can also be run in a one-step procedure from (haloaroylmethyl)triphenylphosphonium bromides 2. Compounds 4–9 are air-stable phosphoranes which undergo formal Wittig-olefination reactions with aldehydes 10 under benzoic acid catalysis. C–C coupling reaction and Wittig olefination can also be performed in a one-step procedure. Preliminary experiments have been performed to carry out the synthesis on a solid support. Applications to the chain elongation and functionalisation of the chain terminus in a C-7 substituted estra-1,3,5(10)-triene 14 and a C-16 substituted estra-1,3,5(10),6-tetraene 12 are shown.