Base‐induced cycloadditions of tosylmethyl isocyanide to a series of isothiocyanates have been investigated. Depending on the reaction conditions, thiazoles 5 and/or imidazoles 7 are obtained, with the thiazoles, in particular, being obtained with high regiospecificity. During the course of this work a high‐yield ring transformation of 5‐amino‐1,3‐thiazoles (5) to imidazole‐5‐thiols (7) was discovered, which has not been previously reported. A number of reactions of 7 are described.
Abstract. Base-induced cycloadditions of tosylmethyl isocyanide to a series of isothiocyanates have been investigated. Depending on the reaction conditions, thiazoles 5 and/or imidazoles 7 are obtained, with the thiazoles, in particular, being obtained with high regiospecificity. During the course of this work a high-yield ring transformation of 5-amino-1,3-thiazoles (5) to imidazole-5-thiols (7) was discovered, which has not been previously reported. A number of reactions of 7 are described.Base-induced reactions of tosylmethyl isocyanide (TosMIC, 1) have been studied with a multitude of simple unsaturated substrates C=X (X = 0, N, S) and with C, C double bonds of Michael acceptors2. As part of a larger programme on reactions of TosMIC with hetero-cumulenic substrates, we report the results obtained with a series of isothiocyanates. With the C=X and C=C substrates mentioned above, TosMIC anion normally reacts in a regiospecific fashion to give azoles, azolines or reaction products thereof2. The same is true for the reaction with CS,, which gives 4-tosyl--1,3-thiazole-5-thioIs in high yield as the only product3. Of interest is the fact that CS, is the only heterocumulene of which reaction with TosMIC has been reported.So far, very few reactions of isothiocyanates with carbanions derived from isocyanides, other than TosMIC, have been investigated. With lithiomethyl isocyanide, thiazole derivatives have been obtained, whereas a--1ithiated ethyl isocyanoacetate has provided oxazole derivatives4". As has been pointed out previously4, (3 + 2)--cycloadditions of a-isocyano carbanions to unsymmetrical
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