SRN1 Reactions of 7 Iodobicyclo[4.1.0]heptane in DMSO by the SRN1 Mechanism. A Novel Stereoselective C-C bond formation on Cyclopropane rings.

NAZARENO M. A.; ROSSI, R. A.

TETRAHEDRON

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1994 vol. 50 p. 9267 - 9274

0040-4020

The photostimulated reaction of 7-iodobicyclo[4.1.0]-heptane (7-iodonorcarane, 1, a mixture of ca. 1:1 of the exo:endo isomers) with acetophenone enolate ion 2 in DMSO at 60°C gave the substitution products 3a (exo) and 3b (endo) in 87% yield (with an exo:endo ratio of 16). In the dark at 60°C, not only the ipso substitution products 3a and 3b (51%), but also the cine substitution product 4 were formed (20%) by an elimination-addition reaction. In the dark and at room temperature there is no reaction. It is suggested that 1 reacts with 2 by a photostimulated as well as a thermal (60°C) SRN1 reaction to give the ipso products 3,with a 3a:3b ratio of ca. 15–23, showing a stereoselectivity of the 7-norcaranyl radicals in the coupling reaction with 2. More selectivity of 1 with 2 was found in the photostimulated reaction in liquid ammonia (at −33°C), with a 3a:3b ratio of ca. 55, although in lower yields (37%). The photostimulated reaction of 1 with 2-acetonaphthone 7 gave only the ipso products (with an exo:endo ratio of 45) and in dark conditions at 60°C there is no reaction with 7. There was no photostimulated reaction of 1 with the anion of nitromethane 9 in DMSO. However, the photostimulated reaction of 1 with 9 in presence of acetone enolate ion 10, the ipso substitution products derived from 9 were formed (entrainment SRN1 reaction), with an exo:endo ratio of ca. 7.3. From competition experiments, 9 was ca. 6.4 times more reactive than 2.