SRN1 REACTIONS OF NUCLEOPHILES WITH RADICAL CLOCKS - RATE CONSTANTS FOR SOME RADICAL NUCLEOPHILE REACTIONS

Treatment of o-3-(but-3-enyloxy)benzene (1) with anions -SPh, -PPh2 and -PO(OEt)2 in ammonia, acetonitrile or dimethyl sulphoxide gives both direct substitution and cyclized products. The formation of the latter confirms the intermediacy of the o-3-(but-3-enyloxy)phenyl radical (2) and confirms that the reactions follow the S(RN)1 pathway. The kinetics of the coupling of the aryl radical 2 were determined by comparison with the known rate of cyclization of 2. Similar experiments with the neopentyl bromide, 6-bromo-5,5-dimethylhex-1-ene, and its 3-oxa derivative also gave cyclized and uncyclized products, thus confirming that the S(RN)1 mechanism applies to the reactions. Approximate rate constants for the coupling of a neopentyl radical with the nucleophiles -SPh and -PPh2 have thus been determined.