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 SRN1 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 SRN1 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.