It has been found that phosphoniosilylation of α,β-unsaturated aldehydes with triphenylphine and trimethylsilyl triflate at -78°C yields kinetically formed 1-silyloxyallylphosphonium salts which are cleanly rearranged to thermodynamically favored 3-silyloxyallylphosphonium salts upon warming to room temperature. Similar results are obtained with α,β-unsaturated acetals.
β-Functionalization of α, β-unsaturated aldehydes has been achieved by the reaction of 1-alkoxy-2-alkenylenephosphoranes, derived from 1-alkoxyallylphosphonium salts, with various electrophiles such as alkyl halides, acid chlorides, benzyl chloroformate, and benzenesulfenyl chloride, followed by removal of triphenylphosphine in five-step, one-pot procedure.
A complete regiocontrol has been found in the reaction of 1-alkoxy-2-alkenylenephosphoranes with aldehydes. The reaction of 1-alkoxy-2-alkenylenephosphoranes with aldehydes gives α-adducts, whereas the reaction in the presence of trimethylsilyl triflate gives $\gamma$ -adducts.
Reaction of 1-alkoxy-2-alkenylenephosphoranes with activated olefins such as vinyltriphenylphosphonium bromide, phenyl vinyl sulfone, and diphenylvinylphosphine oxide proceeds to afford functionalized cyclopropane derivatives which can be subjected to further reaction of ring expansion to give α -methylenecyclopentanones and substituted furans via alkoxy-accelerated rearrangement.
Also, regiochemistry in reaction of direct displacement of 1-methoxy-allyltriphenylphosphonium salt with nucleophiles via easy removal of triphenylphosphine has been studied.
α,β-불포화 알데히드는 -78°C 저온에서 트리페닐포스핀과 트리메틸실릴 트리플레이트와 반응하여 1-실릴옥시알릴포스포늄 염을 형성하고 이 염은 온도가 상승함에 따라 보다 안정한 3-실릴옥시알릴포스포늄 염으로 변환되며, α,β-불포화 아세탈의 경우도 같은 현상이 관찰되었다.
1-알콕시알릴포스포늄 염으로부터 유도된 알릴 일리드와 여러가지 친전자성 치환체들과의 저온반응을 통하여 α,β-불포화 알데히드의 β위치에 알킬, 카르보닐, 설페닐 그룹등의 새로운 관능기를 도입할 수 있었다. 또 이 일리드와 알데히드와의 반응은 α-생성물을 만들었으나 트리메틸실릴 트리플레이트의 존재 하에서는 정 반대의 위치 선택성을 가지고 $\gamma$-생성물을 형성하였다. 한편, 활성화된 올레핀들과의 부가반응에 이은 자리옮김 고리확대화반응을 통하여 환상케톤 화합물과 퓨란 화합물들을 합성할 수 있었다.
