Rh-Catalyzed Highly Enantioselective Hydroalkynylation Reaction of Norbornadiene Derivatives
作者:Baomin Fan、Jianbin Xu、Qingjing Yang、Sifeng Li、Hualei Chen、Shanshan Liu、Lu Yu、Yongyun Zhou、Lin Wang
DOI:10.1021/ol402804t
日期:2013.12.6
The complexes of various Rh precusors with ferrocenyl chiral ligand (R,S)-Cy2PF-PPh2 were found effective catalysts for the asymmetrichydroalkynylation reaction of norbornadiene derivatives. When RhCl3·3H2O was employed, good yields (up to 98%) and high enantioselectivities (up to >99.9% ee) could be obtained for the reactions of a broad scope of substrates.
Photoinduced cycloadditions of 1-acetylisatin (1) with alkenes 2â7 give spiroxetanes 8â21 respectively in moderate to high yields, displaying a typical triplet nâÏ* reactivity for 1. The regioselectivity and diastereoselectivity of the reactions depend on the reaction mechanism. In reactions with alkenes of high oxidation potential (2 and 4) where single-electron transfer (SET) processes with triplet excited 1 are not involved, the regioselectivity can be rationalized by consideration of frontier molecular orbital interactions of the two addends, and the SalemâRowland rules for diradical intersystem crossing explains the diastereoselectivity. For the more electron-rich alkenes, e.g.5â7, SET processes with 31* and ion-radical pair formation are energetically feasible, and the cycloaddition regioselectivity is dependent on charge and spin-density distribution in the ion-radicals and the diastereoselectivity is also decided by ion-radical pair collapse.
Synthesis of air‐stable poly(benzonorbornadiene)s via ring‐opening metathesis polymerization
作者:Huijin Lee、Cheoljae Kim
DOI:10.1002/pol.20220677
日期:——
Herein, air-stable poly(benzonorbornadiene) was synthesized via ring-openingmetathesispolymerization. Conventional poly(benzonorbornadiene) easily decomposed in the presence of molecular oxygen owing to the generation of radicals at allylic and benzylic hydrogens. However, our sterically bulky aryl-group substituents of polymers physically blocked the access of oxygen at these positions. The resulting