Reactions of phosphavinyl Grignard reagents with aldehydes:: synthesis, characterisation and further reactivity of β-phosphaallylic alcohols

The reactions of the phosphavinyl Grignard reagents, Z-[RP= C(Bu-t) MgCl(OEt2)], R = cyclohexyl (Cy) or cyclopentyl (Cy-p), with benzaldehyde have afforded the beta-phosphaallylic alcohols, Z- RP=C(Bu-t) C(H)(OH) Ph, after quenching with methanol. This methodology has been successfully applied to a series of other alkyl, aryl and functionalised aldehydes. The beta-phosphaallylic alcohol, Z- CyP= C(Bu-t) C(H)(OH) Ph, undergoes unusual reactions with ZnEt2, M{N(SiMe3)(2)} (M = Na or K) and Sn{N(SiMe3)(2)}(2) to give three isomers (Z, Z-, Z, E- and E, E-) of the bis(alkenyl) diphosphine mono-oxide, PhC(H)=C(Bu-t) P(Cy) P(= O)(Cy) C(Bu-t)= C(H) Ph. By contrast its reaction with Ti(OPri)(4) led to the formation of the secondary phosphine oxide, Z-CyP(H)(= O) C(Bu-t)= C(H) Ph. A facile synthesis of the phosphaalkenes, E- RP=C(H) Bu-t, R = Cy or mesityl (Mes), is also reported, as is an unusual tungsten complex of one of these, [{W(CO)(4)[eta(1)- P,eta(2)-P= C - CyP= C(H) Bu-t]}(2)]. The X-ray crystal structures of seven of the reported complexes are discussed.