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Reduction of 3-furoic acid by lithium in ammonia at -33" proceeds with 8-elimination and ring opening and consumption of four equivalents of metal to give (3) and (4). Other products (1) and (2) have been observed from reduction in the presence of a proton source. Miwa and coworkers1 have recently reported the reduction of 3-furoic acid under classical Birch conditions (sodium-ammonia-alcohol). The products isolated were acetals of type (1) formed by acid-catalysed addition of alcohol to the reduction product (2) on w0rkup.l We now find that when no proton source is present, 3-furoic acid consumes four equivalents of lithium at 33" giving, on quenching with ammonium chloride, the hydroxy lactone (3) characterized by its spectral data, as well as its 2,4-dinitrophenylhydrazone deri~ative.~ Ethoxy lactones (4) were also isolated in varying amounts; they result from the workup conditions (continuous extraction into CHC1, from the acidified reaction mixture). The ethers (4) showed two g.1.c. peaks in the ratio of 2 : 1 but their separation and purification was precluded by the ready conversion of the pure isomers into an equilibrium mixture. The chemistry of both (3) and (4) has been discussed in some detail.2 The presumed reaction pathway is shown in Scheme 1. As shown by Miwa' the reduction takes place as for an isolated a,/?-unsaturated acid. We feel the difference in the reaction course lies in the relative rate of protonation of the dianionic intermediate (5) by alcohol as opposed to ammonia (the presumed proton source in our system); the basicity of (5) contrasts to the corresponding dianion from benzoic acid which is Kinoshita, T., Miyano, K., and Miwa, T., BUN. Chem. Soc. Jpn, 1975, 48, 1865. Salmon-Legagneur, F., and Le Goff, Y., Bull. Soc. Chim. Fr., 1965, 1761. Short Communications protonated relatively slowly in the presence of methanoL3 There is precedent in the literature for p-elimination of the ether grouping4 under our conditions.

Catalysed gas phase decompositions. XXX. Cyclopropane and boron tribromide