1,3-hydrogen shift in phosphapropenes. Suprafacial sigmatropic rearrangements

Ab initio molecular orbital calculations at the QCISD(T)/6-311+ +G(d,P)//MP2/6-31G(d,p)+ZPE level show that the suprafacial 1,3-hydrogen shifts in the 1-phosphapropene-vinylphosphine (H3C-CH=PH half arrow right over half arrow left H2C=CH-PH2) and degenerate 1,3-diphosphapropene (H2P-CH=PH half arrow right over half arrow left HP=CH-PH2) rearrangements do not only exist but they also compete favourably with the corresponding antarafacial pathways.