Stereospecific cyclodimerization of 1-methylphosphole 1-oxide: a theoretical study

PM3 semiempirical calculations on the transition states for the cyclodimeri zation of 1-methylphosphole oxide (1, Y = Me) suggest the selective formati on of product A (2, Y = Me) that is one of the eight possible isomers. Ab i nitio calculations at the 3-21G* level of theory go even further by justify ing the specific formation of isomer A (2, Y = Me) that is the exclusive pr oduct of the syntheses. The dimerization seems to be directed by kinetic fa ctors. Calculations on the HOMO-LUMO orbital interactions also confirm the preference for the formation of isomer A (2, Y = Me) where the phosphole ri ngs are joined with the endo fusion and where at both phosphorus atoms the oxygen of the phosphoryl group is projected to the center of the system. (C ) 1999 Elsevier Science S.A. All rights reserved.