Vinyl isothiocyanate

Thiols react directly with non-activated alkynes [15] and with 1-alkynyl thioethers [16] to yield alkenyl thioethers in good yield (>76%), whereas thiocyanate anions only add to non-activated alkynes under acidic phase-transfer catalytic conditions on the addition of mercury(II) thiocyanate. Terminal alkynes are converted into vinyl thiocyanates, but disubstituted alkynes also form vinyl isothiocyanates [17]. Major by-products are the ketones formed by solvolysis of the alkynes. 

The other major approach to systems of this type is cycloaddition of cumulene ylides with vinyl isocyanate and vinyl isothiocyanate. Thus, Ph3P=C=C=0 reacts with these two reagents to give 160 and 161 respectively while the corresponding reactions of Ph3P=C=C=NPh afford 162 and 163 <88T543>. By using styryl isothiocyanate with the ketene ylide, 164 was obtained. 

Decomposition of a different type is observed on irradiation of the 3-thiazoline-2-thione (225) resulting in loss of sulfur and the formation of the vinyl isothiocyanate (226)181 further irradiation yields the isoquinoline-1-thione (227). 

Mono- and 1,2-di-substituted alkenes react with PhSeQ/Hg(SCN)2 in benzene (0.5-96 h, at 20 C), giving -tra/if-phenylselenoalkyl isothiocyanates in 70-94% yields.2 Terminal alkenes generally give the product with the selenium terminal (an exception is the prc uct from Bu CH H2) internal alkenes show the expected stereochemistry (cis to threo, trans to erythro). Oxidation to selenoxides could be achieved cleanly only with ozone, and the products cis eliminate in the usual manner to give predominantly the vinylic isothiocyanates (Scheme 73). 

Another method to prepare tetramisole involves reaction of 2-bromo-l-phenylethylamine (31) with vinyl isothiocyanate in methylene chloride at temperatures below 5 C, followed by treatment with mercuric acetate to form tetramisole (3) [24] (Scheme 5). 

The incorporation of a 2-aza-1,3-diene into reactive systems including N-arylketenimines,653,66 N-arylvinylketenimines,656,66 aryl and vinyl isocyanates,67,68 vinyl isothiocyanates,68 and vinyldiimides69 has been shown to provide 2-aza-l,3-diene systems capable of participating in [4 + 2] cy-... 

The more common triazine to pyridine ring transformation is illustrated by the formation of pyridines by reaction of 2,5,6-triethoxycarbonyl-1,2, -triazine with both alkynes and enamines.30,31 The addition of vinyl isocyanate to 1-diethylamino-propyne gives mainly the pyridone (1 ) as a result of initial (2+2) cycloaddition followed by rearrangement the thiopyridone (15) is however formed from the corresponding reaction with vinyl isothiocyanate as a consequence of a (A+2)cycloaddition reaction.32... 

Mercury(II) thiocyanate has been found to catalyze addition of thiocyanic acid to alkynes, the structure of which apparently determines the nature of the products. Vinyl isothiocyanates were obtained from symmetrically disubstituted alkynes whereas vinyl... 

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