Isothiocyanates, alkyl, reaction with

Cycloadditions of isocyanates and their derivatives with vinyiaziridines were first reported by Alper and coworkers. From their previous studies of cydoadditions to vinylepoxides or alkylaziridines, they investigated cydoadditions to vinyiaziridines and found that such reactions with isocyanates, carbodiimides, or isothiocyanates in the presence of catalytic amounts of Pd(OAc)2 (2 mol%) and PPh3 (10 mol%) at room temperature afforded five-membered ring products 249 in 34—97% yields (Scheme 2.61) [91]. When an aziridine 247 possessing an alkyl substituent at the... 

Diamines can also react with only one equivalent of isothiocyanate to form bi-functionnal amine-thiourea ligands 59-68% yields obtained for several alkyl isothiocyanates. However, reaction of phenyhsocyanate with 1,2-diamines could also lead to the formation of the guanidine derivative by cyclisation and elimination of H2S (Scheme 4) [42,43]. 

Alkyl and glycosyl isocyanates and isothiocyanates are produced in good yield under phase-transfer catalytic conditions using either conventional soluble catalysts or polymer-supported catalysts [32, 33]. Acyl isothiocyanates are obtained under similar conditions [34]. A-Aryl phosphoramidates are converted via their reaction with carbon disulphide under basic conditions into the corresponding aryl isothiocyanates, when the reaction is catalysed by tetra-n-butylammonium bromide [35]. 

When the more reactive sulfonyl isothiocyanates are used as 1,3-dipolarophiles 4-alkyl-5-sulfonylimino-A2-l,2,3,4-thiatriazolines are readily prepared at room temperature by reaction with alkyl azides.64,65 The thiatriazolines are obtained in 50-75% yield. Their structures are deduced from NMR, IR, and mass spectral data and degradation experiments. Thus thermal decomposition at moderate temperature (45°-80°) in inert solvents (dry toluene, CC14, acetone) furnished the corresponding carbodiimides [Eq. (22)]. These were identified by their... 

Isothiocyanates react much slower with aminothiatriazoles 87 and require the presence of 4-dimethylaminopyr-idine (DMAP) as a basic catalyst <1989JPR115, 1992JOC1671>. In the case of the parent compound 90, trithiadi-azapentalenes 108 are formed. The substituted 5-aminothiatriazoles (R = alkyl or aryl) 87 are more reactive and afford thiourea derivatives 109 in the reaction with 2 equiv of isothiocyanates (Scheme 26). 

Disubstituted iminothiatriazolines may be formed by reaction of alkyl azides and aryl isothiocyanates but the reaction is relatively slow and the thiatriazoline formed undergoes further reaction with the isothiocyanate present (Section 4.28.2.3.l(iii)). 4-Alkyl-5-sulfonyliminothiatriazolines (73) are readily obtained when the more reactive sulfonyl isothiocyanates are treated with alkyl azides at room temperature (equation 47) (73JOC2916, 74JA3973). 

The reaction between alkyl azides and isothiocyanates produces an isolable thiatriazoline (205 Scheme 43), which was thought to lose N2 on thermolysis to give an unstable intermediate (206), since this has apparently been trapped by a number of C=S containing compounds to give 1,2,4-dithiazolidine derivatives (76JHC883). Further reaction with isothiocyanate, however, occurred in three different ways, and depended on the nature of R3NCS, and on the reaction conditions. For ArNCS, the relative amounts of products (207),... 

Exposure of the alkyne 426 to BuLi in the presence of /-BuOK, followed by reaction with ethyl isothiocyanate, gave the intermediate 427, which was subsequently alkylated and cyclized to the pyrrole 428 (Scheme 53) <1999EJ02663>. 

Like other heterocyclic iV-oxides, imidazole 3-oxides 1063 react with AC2O to give the corresponding imidazolones 1064 and 1065 (Scheme 257). TMSCN transforms 1063 into imidazole 2-carbonitriles 1066, whereas alkyl thiones convert 1063 to 1067 <2000HCA728, 1998HCA1585, 2002AGE2290>. The 2-aminoimidazoles 1068, formed from the reactions with either isocyanate or isothiocyanate, react further with isocyanates to form ureas but are inert toward thiourea formation. In contrast to nonaromatic imidazole A -oxides (nitrones), oxides 1063 react with DMAD to form butanedioates 1069, rather than the (putative) [3-1-2] adduct <2000T5405>. 

---