| Abstract
| - 2-Halophenyl ketones 1a−e (1a, o-IC6H4COCH3) undergo carbocyclization with alkyl propiolates(2a, CH3(CH2)4C⋮CCO2CH3; 2b, TMSC⋮CCO2Et 2c, CH3C⋮CCO2CH3; 2d, CH3OCH2C⋮CCO2CH3;2e, CH3(CH2)3C⋮CCO2CH3; 2f, PhC⋮CCO2CH3; and 2g, (CH3)3C⋮CCO2CH3) in the presence ofNi(dppe)Br2 and zinc powder in acetonitrile at 80 °C to afford the corresponding indenol derivatives3a−m with remarkable regioselectivity in good to excellent yields. The nickel-catalyzed carbocyclization reaction was successfully extended to other simple disubstituted alkynes. Thus, thereaction of 2-halophenyl ketones 1a−e with disubstituted alkynes (2h, PhC⋮CPh; 2i, CH3C6H4C⋮CC6H4CH3; 2j, CH3CH2C⋮CCH2CH3; 2k, PhC⋮CCH3; 2l, TMSC⋮CCH3; and 2m, PhC⋮C(CH2)3CH3)proceeded smoothly to afford the corresponding indenols 4a−t in good to excellent yields. Forunsymmetrical alkynes 2k−m, the carbocyclization gave two regioisomers with regioselectivitiesranging from 1:2 to 1:12 depending on the substituents on the alkyne and on the aromatic ring ofhalophenyl ketone. A possible mechanism for this nickel-catalyzed carbocyclization reaction is alsoproposed.
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