PHOTOSTIMULATED REACTIONS OF NEOPENTYL IODIDES WITH CARBANIONS IN DMSO BY THE S(RN)1 MECHANISM

Neopentyl iodide, 1, reacted under photostimulation with several carba nionic nucleophiles in DMSO. With acetone enolate ion only reduction a nd dimerization occurred, but good yields of substitution products hav e been obtained with acetophenone, 5, and anthrone, 9, anions as nucle ophiles. Nitromethane anion, 7, does not react with 1 under irradiatio n, but good yields of the substitution products are obtained when the photostimulated reaction is carried out in the presence of acetone eno late ions (entrainment reaction). Inhibition experiments by p-dinitrob enzene and by the radical trap TEMPO, suggest that these reactions occ ur by the S(RN)1 mechanism of nucleophilic substitution. The photostim ulated reaction of 1,3-diiodo-2,2-dimethylpropane, 15, with 5 gave the disubstitution product 17 and the reduced monosubstitution product 18 . It has been found that the monosubstitution product 16 (in which iod ine is retained) is not an intermediate of these reactions. 1-iodoadam antane, 12, is more reactive (ca. 4.9 times) than 1 in competitive exp eriments toward 5 and under photostimulation.