Phosphane-ene chemistry: the reactivity of air-stable primary phosphines and their compatibility with the thiol-ene reaction

Air-sensitive and air-stable primary phosphines (RPH2) were compared for their ability to undergo photo-initiated phosphane-ene chemistry with 1-hexene. Despite their increased air-stability, the primary phosphines displayed equal to or greater reactivity when compared to air-sensitive alkyl or aryl analogues. The phosphane-ene reaction was also performed in the presence of 1-octanethiol to determine whether thiol-ene and phosphane-ene chemistries could proceed simultaneously. It was determined that the phosphane-ene process takes precedence over thiol-ene as P-H bond conversion was independent of thiol concentration. Tertiary phosphine (R3P) and some secondary phosphine (R2PH) products were found to react with thiols under experimental conditions to create phosphine-sulfides (P-S), but this chemistry only proceeded at low P-H bond concentrations. These results suggests that hydrogen transfer reactions take precedence over P-S formation and demonstrate the unique relationship between phosphane-ene and thiol-ene chemistry.