Density functional theory study on the regioselective Diels–Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with some 1,3-butadiene derivatives (RCHCHCHCH2, R = F, Cl, CH3 and SiH3) have been reported. Two different pathways were considered: i) in the absence of coordinating reagent, ii) in the presence of AlCl2Me and BCl2Me as a co-ordinated reagent to the σ2, λ3 P atom. Also with considering the position of R group in the obtained cycloadducts, two model DA reactions were studied, (R/P, 1, 2) and (R/P, 1, 5).
