Transition-metal-catalyzed cleavage of carbon&ndash;selenium bond and addition to alkynes and allenes

Fujiwara, Shin-ichi; Toyofuku, Masashi; Kuniyasu, Hitoshi; Kambe, Nobuaki

doi:10.1351/PAC-CON-09-11-13

Pure Appl. Chem., 2010, Vol. 82, No. 3, pp. 565-575

http://dx.doi.org/10.1351/PAC-CON-09-11-13

Published online 2010-02-18

Transition-metal-catalyzed cleavage of carbon–selenium bond and addition to alkynes and allenes

Shin-ichi Fujiwara¹, Masashi Toyofuku², Hitoshi Kuniyasu² and Nobuaki Kambe²*

¹ Department of Chemistry, Osaka Dental University, Kuzuha-hanazonocho 8-1, Hirakata Osaka 573-1121, Japan
² Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan

Abstract: This account summarizes our recent results on transition-metal-catalyzed cleavage of C–Se bond and addition to unsaturated hydrocarbons such as alkynes and allenes. Pd(0)‑catalyzed intramolecular carbamoselenation of alkynes forms four- to eight-membered α-alkylidenelactams. Interestingly, four-membered ring formation is faster than five- and six-membered ring formation. Intramolecular vinylselenation of suitably structured alkynes offers pathways to conjugated δ-lactam frameworks. Electron-withdrawing groups on the vinyl moiety are essential to promote this reaction. Intermolecular 1,2-addition of selenol esters onto allenes proceeds with excellent regioselectivity and high stereoselectivity in the presence of a Pd(0) catalyst, producing functionalized allyl selenides. In addition, Pd(0)‑catalyzed intramolecular selenocarbamoylation of allenes gives α,β-unsaturated γ- and δ-lactams with perfect regioselectivity. The scope and limitations, as well as reaction pathways, are discussed.