Facile, Highly Stereoselective Synthesis of Spiro[cyclopropane-1,3′-indolin]-2′-ones and Spiro[cyclopropane-1,2′-indane]-1′,3′-diones Containing Trifluoromethyl Group

In this paper, the new synthesis of trans-2,3-dihydro-spiro[cyclopropane-1,3'-indolin]-2'-one and trans-2,3-dihydro-spiro[cyclopropane-1,2'-indane]-1',3'-dione containing CF3 group was reported. Arsonium bromides 2 reacted with 2-(4-(trifluoromethyl)benzylidene)-1H-indene-1,3(2H)-dione (1) or 3-(4-(trifluoromethyl)benzylidene)indolin-2-one (3), using KF or K2CO3 as base in CH2Cl2, to provide the target products with high stereoselectivity in good yields. The relative stereochemistry of key compounds has been determined by single-crystal X-ray structural analysis and H-1-H-1 NOESY technique. The mechanism was also proposed.