60930-93-0

A convenient procedure for preparing N-mono- and NN-di-substituted cyanamides from cyanogen bromide has been developed.N,N-Disubstituted thioureas, obtained from the cyanamides, were condensed with α-bromo-α-cyanoketones to give 5-cyano-2-(N,N-disubstituted amino)thiazoles and with α-bromo-ketones to give 2-(N,N-disubstituted amino)thiazoles.Substitution in the latter products afforded 5-trifluoroacetyl- and 5-nitro-2-(N,N-disubstituted amino)thiazoles; nitration is greatly facilitated by the presence of a 4-aryl group.The average values of the barriers of rotation of the barriers to rotation of the 2-NR2 groups (ΔG298) in the 5-substituted thiazoles were established by variable temperature 1H n.m.r. spectrometry to be 57.4 kJ mol -1 (5-NO2), 56.2 (5-COCF3), and 51.5 (5-CN).I.r. examination showed that the 5-trifluoroacetyl compounds adopt one rotational form preferentially; this is probably the carbonyl O,S-syn-conformation.

Some γ-bromo-β-oxonitriles 3 react with furan in the presence of silver oxide to form stereoselectively the title compounds 7.Satisfying yields are obtained only with those bromides 3, whose γ-carbon is tertiary or which are monoalkylated both at the α- and γ-carbon atoms.The results are explained by a cycloaddition of 1-cyanoallylium-2-olate intermediates (14) to the 1,3-diene system of the furan.With cyclic γ-bromo-β-oxonitriles (6) two types of cycloadducts were observed: 3-bromo-3-methyl-2-oxocyclohexanecarbonitrile (6b) and 3-bromo-2-oxocyclododecanecarbonitrile (6d) form the tricyclic cycloadduts 10b and d, analogs of the bicyclic adducts 7.With 3-bromo-2-oxocyclohexanecarbonitrile (6a) and 3-bromo-5-tert-butyl-2-oxocyclohexanecarbonitrile (6e), however, the carbonyl oxygen is connected with an α-carbon of the furan to give the tricyclic cycloadducts 12Aa and Ae.The structure endo-2,endo-4-dimethyl-3-oxo-8-oxabicyclooct-6-ene-exo-2-carbonitrile (7eα) was determined by X-ray analysis.