Enantioselective Cycloisomerization of 1,6-Enynes to Bicyclo[3.1.0]hexanes Catalyzed by Rhodium and Benzoic Acid

Abstract

It has been established that a cationic Rh(I)/(S)-Segphos or (S)-DTBM-Segphos complex and benzoic acid catalyze the enantioselective cycloisomerization of 1,6-enynes, possessing carbonyl groups at the enyne linkage, to 2-alkylidenebicyclo[3.1.0]hexanes. The present cycloisomerization may involve site selective γ-hydrogen elimination. The one-pot enantioselective cycloisomerization and lactonization of 1,6-enynes, leading to bicyclic lactones, has also been accomplished.

Construction of Hexahydrophenanthrenes By Rhodium(I)‐Catalyzed Cycloisomerization of Benzylallene‐Substituted Internal Alkynes through C−H Activation

“…This might be due to as ignificant nonbonding interaction between the diethyl group and the methyl group on the allene moiety during the s-bond metathesis [21] leading to B.F or the dibutyl and cyclohexyl derivatives 17 b and 17 c, the s-bond metathesis [21] of A can no longer proceed. This might be due to as ignificant nonbonding interaction between the diethyl group and the methyl group on the allene moiety during the s-bond metathesis [21] leading to B.F or the dibutyl and cyclohexyl derivatives 17 b and 17 c, the s-bond metathesis [21] of A can no longer proceed.…”

“…Then, s-bond metathesis [21] between aC (sp 2 )ÀHb ond on the benzene ring and the C(sp 2 )ÀRh III bond of A would lead to s-allylrhodium intermediate B,which would be in equilibrium with another s-allylrhodium intermediate D via p-allylrhodium intermediate C.R eductive elimination of Rh III would finally give 7 (or 12). Then, s-bond metathesis [21] between aC (sp 2 )ÀHb ond on the benzene ring and the C(sp 2 )ÀRh III bond of A would lead to s-allylrhodium intermediate B,which would be in equilibrium with another s-allylrhodium intermediate D via p-allylrhodium intermediate C.R eductive elimination of Rh III would finally give 7 (or 12).…”

Synthesis of Bicyclo[n.1.0]alkanes by a Cobalt‐Catalyzed Multiple C(sp3)−H Activation Strategy

“…[3] An attractive and complementary strategy is reaction sequences which involve C(sp 3 ) À H activation. [6][7][8] Sato,M ukai, and Tanaka have reported the rhodium(I)catalyzed oxidative cycloaddition of 1,6-enynes followed by rhodacycle-directed C(sp 3 ) À Hb ond activation. [5] However,t he de novo synthesis of cyclopropanes by C(sp 3 )ÀHf unctionalization remains rare.…”

“…[4] Recently,t ransition metal catalyzed direct C(sp 3 ) À Hf unctionalization of cyclopropanes has been well investigated. [6] Another interesting strategy involves oxidative addition of palladium-(0) to arylhalides,H eck-type carbopalladation to form aC -(sp 3 )ÀPd II complex, which enables as ubsequent C(sp 3 )ÀH bond activation. [6][7][8] Sato,M ukai, and Tanaka have reported the rhodium(I)catalyzed oxidative cycloaddition of 1,6-enynes followed by rhodacycle-directed C(sp 3 ) À Hb ond activation.…”

“…[5] However,t he de novo synthesis of cyclopropanes by C(sp 3 )ÀHf unctionalization remains rare. [6][7][8] Sato,M ukai, and Tanaka have reported the rhodium(I)catalyzed oxidative cycloaddition of 1,6-enynes followed by rhodacycle-directed C(sp 3 ) À Hb ond activation. [6] Another interesting strategy involves oxidative addition of palladium-(0) to arylhalides,H eck-type carbopalladation to form aC -(sp 3 )ÀPd II complex, which enables as ubsequent C(sp 3 )ÀH bond activation.…”