Phenoxycarbonyl isocyanate

Liquid carbon suboxide added to a solution of 2-ethylaminothiarole in anhydrous ether at 0°C gives immediate formation of a white precipitate of the mesoionic xanthine (121) (R=H) (130), otherwise prepared by reaction between 2-ethylaminothiazole and phenoxycarbonyl isocyanate (see p. 65 and Ref. 304),... 

The reaction between DBU and phenoxycarbonyl isocyanate afforded a 2,3a,6a-triazacyclohepta[d,e]naphthalene derivative (35) (73GEP2126148). 

The use of phenoxycarbonyl isocyanate for cyclizing an aminoazole in pyridine is well known (p. 289). This reaction may also be effected by refluxing the reactants in a neutral high-boiling solvent. Chlorocarbonyl isocyanate (review [2929, 3802]) is also a very effective reagent for cyclizing such amines. 

Dihydro-2//-l,3,5-thiadiazines containing a ring carbonyl or thiocarbonyl group are synthesized from reaction of thioamides with phenoxycarbonyl isocyanate, dimerization of thiocarbamoylisothiocyanates, or dimerization of carbamoyl isocyanates. The latter two [4-1-2] cycloaddition reactions complement the tabulated list of dienes and dienophiles presented in Table 2 (Section 9.09.9.2). 3,6-Disubstituted-3,4-dihydro-2//-l,3,5-thiadiazines are synthesized by treatment of N-substituted A, Wbis(l//-l,2,3-benzotriazol-l-ylmethyl)-amines with thioamides and zinc bromide (Section 9.09.9.1.3). 

Acylketenes, generated in the thermolysis of 4-oxo-l,3-dioxine derivatives, react with phenylcarbonyl-, methoxycarbonyl-, or phenoxycarbonyl isocyanates by a [4+2] cycloaddition reaction to give 2,4-dioxo-l,3- oxazines. ... 

---