From isothiocyanates

Thioureas give thioxo analogues of a variety of the above syntheses (52JOC542), although these thioxo products are usually prepared from isothiocyanates (Section 2.15.5.2.1). Examples are known in the pyrido-[2,3-[Pg.225]

Other functional groups that are easily differentiated are cyanide (5c =110-120) from isocyanide (5c = 135- 150), thiocyanate (5c =110-120) from isothiocyanate (5c = 125 - 140), cyanate (5c = 105- 120) from isocyanate (5c = 120- 135) and aliphatic C atoms which are bonded to different heteroatoms or substituents (Table 2.2). Thus ether-methoxy generally appears between 5c = 55 and 62, ester-methoxy at 5c = 52 N-methyl generally lies between 5c = 30 and 45 and. S-methyl at about 5c = 25. However, methyl signals at 5c = 20 may also arise from methyl groups attached to C=X or C=C double bonds, e.g. as in acetyl, C//j-CO-. 

Amines, preparation from isothiocyanates, 18, 5 from ketones, 17, 76 m-Aminobenzaldehyde, 13, 28... 

A direct procedure from isothiocyanates and amines using tetrabutylammo-nium thiocyanate (Bu4NSCN) and PhCH2NMe3Br3 affords functionalized 2-aminobenzo-l,3-thiazoles (Scheme 60).143... 

The thiatriazolines (237), which are obtained from isothiocyanates and alkyl azides are potentially masked 1,3-dipoles (see also Section 4.14.6.7) and react with sulfenes to give the sultams (238), probably through the thiapentalene-like transition state/intermediate (239) (Scheme 45) <78JOC4951>. 

Aminothiatriazoles (13) may alternatively be prepared from isothiocyanates and hydrazoic acid (Equation (16)) <77CCC1557, 80CCC2329, 81BSB63>. 

Compounds of molecular formulae (RNCS)20 and (RNCS)2S, for which 1,2,4-thiadiazolidine structures have been considered, are obtainable from isothiocyanate esters on oxidation the latter series is also accessible from dithiocarbamates. 

Isothiocyanate sulfides, (RNCS)2S, arise similarly from isothiocyanates by successive treatment with bromine in anhydrous chloroform, and hydrogen sulfide158,160 or ethanol.161 The phenyl homolog has also been obtained by the action of thiophosgene on diphenyl-thiourea,162 or aluminum chloride on phenyl isothiocyanate.103... 

Imidothioesters are easily obtained through 5-alkylation of thioamides, and we have noted (see Section 2.8.3) a general preparation of such compounds from isothiocyanates via addition of an organometallic and 5-alkylation. 

Regiospecific, Pd(II) catalysed, cycloaddition reactions of azetidines to yield ring-enlarged products include the formation of tetrahydro-2-iminopyrimidines (e.g. 10) by reaction with carbodi-imides (95JOC253) and tetrahydro-l,3-thiazin-2-imines (e.g. 11) from isothiocyanates (95JOC3092). 

Formation of thiourea linkages from isothiocyanates and e-amino groups of lysine residues in proteins... 

A similar reaction has been more recently described by other authors. Thioureas 89—the intermediates in the preceding reaction—were prepared from isothiocyanate 88 and amines. Benzo-TAs 90, which contain substituents on the exocyclic nitrogen atom, were obtained (92MI1) (Scheme 28). 

PHA827). 3-Amino-6-phenylthieno[2,3-<7]pyrimidin-4-one-2(l H)-thione (17) was obtained similarly from isothiocyanate 15 (R1 = C02Et, R2 = H, R3 = Ph) via the thiosemicarbazide 16 (94PHA64). Isothiocyanate 15 [R1 = COPh, R2, R3 = (CH2)4] was reacted with hydrazine hydrate and various primary amines to give directly the 3-substituted 4-phenyl-2-thioxothieno[2,3-c/ pyrimidines 82b (90JHC269). 

Amidoximes (278) yield 5-mercapto-l,2,4-thiadiazoles (279) when treated with carbon disulfide whereas the 5-amino derivatives (280) are obtained from isothiocyanates, as indicated in Scheme 96 <65AHC(5)li9). Products of type (280) are also produced in the reaction between /V-sulfenylamidines (281) and isothiocyanates (Scheme 97). 

I. Ugi (ed.), Isonitrile Chemistry. Academic Press, New York, 1971. Synthesis of heterocycles, from isothiocyanates ... 

The amino alcohols d-50 and l-50 were converted into d-408 and l-408 via coupling with isothiocyanate 7 to give the thiourea d-405 (93%), which was similarly converted into the cyclic isourea d-406 100%) (Scheme 53).98 Conventional O-debenzylation afforded the trehazolin analogue d-407 (96%), which was further characterized as the octa-iV,O-acetyl derivative d-408. Likewise, the diastereoisomer l-407 was synthesized in 91% overall yield by similar reaction sequence, starting from the l-405 (97%) obtained from isothiocyanate 7 and aminotetrol l-50. 

Table 2.2 Cycloadducts derived from Isothiocyanates and Carbodiimides...

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