Acylisothiocyanates

TABLE n-37. 2,S-DISUBSTITUTED AMTNOTHIAZOLES DERIVATIVES FROM ACYLISOTHIOCYaNATES ... 

Lieber et al. have discussed whether the compound obtained from the sodium salt of the thiol and methyl iodide is an A- or an /S-deriv-ative and have proved that it is the /S-derivative by syntheses of this compound from methyl dithiocarbazinate (CHgS—CS—NH—NH2) and nitrous acid. The acyl derivatives are, however, formulated as A-acylthiatriazoline-6-thiones, because they are decomposed to form acylisothiocyanates. Lieber et have shown that thiocyanates... 

Wilson and Li have recently used supported acylisothiocyanates to capture amines as thioureas.40 The latter were then activated using a car-bodiimide reagent, then reacted with a second amine to form guanidine products. An appealing feature of this approach is that hindered and relatively unreactive anilines can be used in the first step due to the electro-philicity of the acylisothiocyanates (Scheme 18). 

The poor reaction with C-terminal proline most likely stems from the fact that proline cannot form the necessary oxazolinone for efficient reaction with the isothiocyanate. Work in our laboratory has obviated the need for oxazolinone formation by the use of diphenyl phosphoroisothiocyanatidate and pyridine. Reaction of this reagent with C-terminal proline directly forms the acylisothiocyanate. Once the acylisothiocyanate is formed, the addition of either liquid or gas phase acid followed by water was... 

The failure of previous methods to derivatize C-terminal proline may be due to the inability of proline to form an oxazolinone, a necessary step in many of the previous methods. The use of DPP-ITC/pyridine for derivatization permits the direct formation of an acylisothiocyanate at the C-terminus without the... 

Once an acylisothiocyanate is formed it can cyciize to a quaternary amine containing thiohydantoin. This thiohydantoin, if protonated with acid, is stabie. If the acid step is eiiminated C-terminal proiine is regenerated. The quaternary amine containing proiine thiohydantoin can be readiiy cleaved with water vapor or aiternativeiy with the siianoiate salt normally used for the cleavage reaction. 

Acylisothiocyanates (221), Rj = Ac, refluxed in alcoholic solution with a-aminoacetonitrile, in the presence of benzaldehyde or its substituted derivatives, afford the corresponding 5-benzylideneaminothiazole derivatives (225) in which Rj = hydrogen or propenyl and Rj = aryl or styryl (Scheme 117 and Table 11-37) (394). 

During the past twelve months a number of new phosphonium betaines and zwitterions has been reported. Reaction of ylides with acylisocyanates or acylisothiocyanates in methanol proceeds via a cyclization yielding pyrimidine substituted triphenylphosphonium salts (5) which can be converted into the corresponding betaines. The crystal structures of triphenylphosphonium-car-boxylate betaines 6 and 7 have been reported. Betaines 6 and 7 were obtained... 

In the synthesis of lipoprotein-associated phospholipase A2 inhibitors reported by Smith and coworkers, the pyrimidonc rings of 24 originated from the condensation of amines with acylisothiocyanate 23 <01BMCL701>. No yields were reported in these transformations. Using similar chemistry, it was also reported that vinylogous carbamate 25 cyclized to fused pyrimidones 26 upon reaction with an isocyanate, isothiocyanate, or dilhioketal <01H115>. 

Acylamino-l-thioethers N-Acylcarboxylic acid thioamides Acylisothiocyanates Cyanothioformic acid esters Methylthiomethyl iminoesters l-(Organothio)alkoximes... 

Acylamino-1 -thioethers N-Acylcarboxylic acid thioamides Acylisothiocyanates Acylthiocyanates N-Acylthioiminoesters N-a-Alkoxycarboxylic acid thioamides... 

Bromine via y -amino-a,) -ethylenecarboxylic acid tbioamides from acylisothiocyanates s. 18, 354 Br... 

Simple one-step synthesis of 4-thiopyrimidines from enamines and acylisothiocyanates... 

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