A process for preparing cis-olefins of the formula ##STR1## where R is alkyl or alkenyl and R.sup.1 is alkyl and alkenyl, both optionally substituted by hydroxy, carbalkoxy or acyloxy, which comprises an ylide solution of the compound R--CH.sub.2 --P.sup.+ (C.sub.6 H.sub.5).sub.3 Br.sup.- in hexaalkyl phosphoric acid triamide and adding an aldehyde of the formula R.sup.1 --CHO.
一种制备式为##STR1##的顺式烯烃的方法,其中R为烷基或烯基,R.sup.1为烷基和烯基,可选择地通过羟基、羰基酯或乙酰氧基取代,该方法包括在六烷基
磷酸三胺中的化合物R-CH.sub.2-P.sup.+(C.sub.6H.sub.5).sub.3Br.sup.-的
亚胺溶液中,加入式为R.sup.1-CHO的醛。