Highly Regioselective Construction of Spirocycles via Phosphine-Catalyzed [3 + 2]-Cycloaddition
摘要:
A direct entry to spirocycles with low to moderate regioselectivity was achieved by triphenylphosphine-catalyzed [3 + 2]-cycloaddition of active exo-methylenecycles (1) and ethyl 2,3-butadienoate (2). The regioselectivity of the reaction was greatly improved by using the bulky tert-butyl ester of the 2,3-butadienoate (5). The regioselectivity of the reaction was further enhanced by using the tert-butyl 2-butynoate as the substrate. This protocol provided an efficient entry to the skeleton of spirocarbocycles, especially spiro[4.n]alkanes.
Nucleophilic 5-endo-trig cyclizations of N-homoallylic sulfonamides: a facile method for the construction of pyrrolidine rings
作者:Junji Ichikawa、Guillaume Lapointe、Yu Iwai
DOI:10.1039/b618251h
日期:——
5-endo-trig cyclizations proceed in N-homoallylsulfonamides bearing a CF(3), CCl(3), CO(2)Et or CN group at the C-3 position, via an intramolecular S(N)2'-type or addition reaction to construct pyrrolidine rings, even though the system allows a more favorable 5-exo-trig pathway.
Highly Regioselective Construction of Spirocycles via Phosphine-Catalyzed [3 + 2]-Cycloaddition
作者:Yishu Du、Xiyan Lu、Yihua Yu
DOI:10.1021/jo026111t
日期:2002.12.1
A direct entry to spirocycles with low to moderate regioselectivity was achieved by triphenylphosphine-catalyzed [3 + 2]-cycloaddition of active exo-methylenecycles (1) and ethyl 2,3-butadienoate (2). The regioselectivity of the reaction was greatly improved by using the bulky tert-butyl ester of the 2,3-butadienoate (5). The regioselectivity of the reaction was further enhanced by using the tert-butyl 2-butynoate as the substrate. This protocol provided an efficient entry to the skeleton of spirocarbocycles, especially spiro[4.n]alkanes.