... 2; I. Fleming; Frontier Orbitals and Organic Chemical ReactionsJ. Wiley, Inc, N. Y (1976). 3; MDNO calculations indicate that the introduction of a phenylsulfonyl group causes a significant lowering of the LUMO energy level compared with allene and the largest LUMO coefficient resides on the central carbon and the next on the carbon bearing the phenylsulfonyl group. 4; A. Padwa, SP Carter, U. Chiacchio, DN Kline; Tetrahedron Lett. (1986), p. 2683. ...