title: Asymmetric Diels-Alder reaction with >C=P- functionality of the 2-phosphaindolizine-η(1)-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results.
abstract: The Diels-Alder reaction of the 2-phosphaindolizine-η(1)-P-aluminium(O-menthoxy) dichloride complex with dimethylbutadiene was investigated experimentally and computationally. The >C=P- functionality of the complex reacts with 2,3-dimethylbutadiene with complete diastereoselectivity to afford [2 + 4] cycloadducts. Calculation of the model substrate, 3-methoxycarbonyl-1-methyl-2-phosphaindolizine-P-aluminium(O-menthoxy) dichloride (7a), at the DFT (B3LYP/6-31+G*) level reveals that the O-menthoxy moiety blocks the Re face of the >C=P- functionality, due to which the activation barrier of the Diels-Alder reaction of 7a with 1,3-butadiene, involving its attack from the Si face, is lower. It is found that in this case, the exo approach of the diene is slightly preferred over the endo approach.
authors.affiliation: Department of Chemistry, University of Rajasthan, Jaipur 302004, India.
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Jangid
authors.forename: Nidhi
authors.initials: N
authors.lastname: Sogani
authors.forename: Neelima
authors.initials: N
authors.lastname: Gupta
authors.forename: Raj Kumar
authors.initials: RK
authors.lastname: Bansal
authors.forename: Moritz
authors.initials: M
authors.lastname: von Hopffgarten
authors.forename: Gernot
authors.initials: G
authors.lastname: Frenking
keywords: >C=P– functionality; DFT calculations Diels–Alder reaction; aluminium(O-menthoxy) dichloride; asymmetric synthesis