Isothiocyanates 5-hydroxy

Hydroxy-THISs add regioselectively to the C=N bonds of isocyanates and isothiocyanates producing stable adducts (Scheme ID (19). 

Hydroxy-THISs add regioselectively to the C=N bonds of isocyanates or isothiocyanates. The initially formed cycloadducts eliminate carbonyl sulfide with formation of 4-hydroxy- or 4-mercaptoimidazolium hydroxide inner salts (21) (Scheme 21). 4-Hydroxyimidazolium hydroxide... 

Acylisocyanates or isothiocyanates undergo cycloaddition with 5-hydroxy-THISs under so mild conditions that isolation of the initial adducts becomes possible (23). In cycloaddition reactions the 5-hydroxy-THISs can be replaced by their precursors (23). 

The 5-acylamino-THISs react with alkynes in a way already exemplified for 5-hydroxy-THISs. Pyrroles are formed under elimination of isothiocyanate (Scheme 29) (37). 5-Acylamino-THISs are readily bromi-nated in the 4-position (21). 

It is worth noting that the 2-pyridone 42 (99MI1) and thione 43 (88H(27)733), which could react in either of the two ways as shown, with an isocyanate or isothiocyanate and with a nitrile respectively, actually give a one-carbon insertion. There is a case of formation of 2,3 and 3,4 bonds in the preparation of 8-hydroxy-triazolopyridine 44 (83MI1). 

Isocyanine, hydride ion transfer in, 43 Isoindoles, from 5-hydroxy-THlSs, 9 Isothiocyanates, adducts with thiazolium salts, 35... 

On the other hand, refluxing 9 in formic acid for 5 h afforded the N-formyl derivative 11 in high yield. Acetylation of 9 by refluxing in acetic acid, afforded acetic acid N -(2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-acetyl)-hydrazide 12 in good yield. Compound 13 was also obtained by refluxing 9 with 3-(2-bromoacetyl)-4-hydroxy-2H-chromen-2-one in ethanol. Reaction of compound 9 with phenyl isothiocyanate in ethanol at room temperature gave 4-phenyl-1 - (7-hydroxy-2-oxo-2 H-chromen-4-acetyl- )thiosemicarbazide 14. 

The pyrirnido[ 1,6-/z [3,l [benzoxazin-1 -thionc 230 was formed in a tandem [5+1, 6+0 (/ )] cyclization as depicted in Scheme 38. The first step is the nucleophilic attack of the aniline nitrogen of 228 (X = O) onto the isothiocyanate and then onto the aldehyde carbon to form l-(2-hydroxymethyl)phenyl-6-hydroxy-tetrahydropyrimidine-2-thione, which cyclizes to 230 <2005BMC3185>. 

In a different study, anthracene, phenanthrene, perylene 93 (Fig. 31), and 2,7-di-tert-butylpyrene underwent regioselective oxidative-substitution reactions with iodine(III) sulfonate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene, in conjunction with trimethylsilyl isothiocyanate, led to thiocyanation of the PAH nucleus. 

Diazo(trimethylsilyl)methyl lithium (3) was found to be the reagent of choice for the synthesis of azoles from heterocumulenes (Scheme 8.43). The reaction is typically carried out in ether at 0-20 °C. Thus, alkyl- (or aryl-)substituted keteni-mines are transformed into 1,2,3-triazoles 188 (246), while C-acceptor-substituted ketenimines yield either 4-aminopyrazoles 189 or 1,2,3-triazoles, depending on the substituents (247). Isocyanates are converted into 5-hydroxy-1,2,3-triazoles 190 (248). Reaction of 3 with isothiocyanates are strongly solvent dependent. 

Bromo- or -hydroxy-isothiocyanates react with amines to give 2-amino- or 2-imino-l,3-thiazepines depending on the nature of the amine (710PP27,71CJC971). 

Isatoic anhydride can be used as a versatile synthon for the synthesis of a diverse set of molecules. The isatoic anhydride can be reacted with amines, amides, hydrazides, isothiocyanates, diketo substrates, aminoacids, amino-, thio or hydroxy anilines, as well as in a three-component reaction with aldehydes and amines to form a large set of diverse pharmacophores. 

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