No abstract

Effect of the number and positions of the methoxycarbonyl substituents in 2‐phosphaindolizine on the feasibility of its Diels–Alder (DA) reaction with 1,3‐butadiene has been investigated theoretically at the density functional theory (DFT) level. Among the series of four differently substituted 2‐phosphaindolizines, 3‐methoxycarbonyl‐2‐phosphaindolizine does not undergo the DA reaction due to the highest activation barrier (29.49 kcal mol−1) and endothermicity, whereas the activation barrier of the corresponding reaction of 1,3‐bis(methoxycarbonyl)‐2‐phosphaindolizine is lowest (22.43 kcal mol−1) with exothermicity making it possible to occur. This reactivity trend is corroborated by FMO energy gaps as well as by global electrophilicity powers of the reactants. Copyright © 2008 John Wiley & Sons, Ltd.

Organo-phosphorus compounds S 0080Diastereo-and Regioselective Diels-Alder Reactions of 2-Phosphaindolizines.-The reaction of substrates (I) with dienes (II) in the presence of sulfur affords the addition products with complete diastereoselectivity and with 100% regioselectivity in the case of isoprene (IIc). -(BANSAL*, R. K.; GUPTA, N.; KUMAWAT, S. K.; DIXIT, G.; Tetrahedron 64 (2008) 27, 6395-6401; Dep. Chem., Univ. Rajasthan, Jaipur 302 004, India; Eng.) -Bartels 47-178