Cyclohexene isocyanate

A vinyl isocyanate, which may be considered as a 1,4-dipolar system, will react with an enamine to give a pyridone. Octahydrophenanthridone results when cyclohexene isocyanate and a cyclohexene enamine are used (J.H. Rigby and H. Balasubramanian, J, org. Chem., 1984, 49, 4569). 

Phosgene reacts exothermically with thiirane in two steps (Scheme 36) (77MI50602). 3,5-Dinitrobenzoyl chloride and benzoyl fluoride initiate polymerization of thiirane. A novel reaction of benzoyl isocyanate or trichloroacetyl isocyanate, which yields ethylenethiol derivatives from epithiochlorohydrin (2-chloromethylthiirane), 2-methylthiirane or cyclohexene episulfide, has been reported (Scheme 37) (71BAU2432). 

The similar addition of a mesityl-substituted isocyanate to 1-morpiiolino-cyclohexene gave the dihydrothiazinone 233, which is in ring-chain equilibrium with 234. In the attempted preparation of the rerr-butyl-substituted derivative, the tetrahydrobenzothiazinone 235 was formed by loss of morpholine (81CB549). 

Two other observations are noteworthy. First, the yield of isocyanate (9) produced on photolysis of 7 in methylene chloride (an inert solvent) is 40%. Photolysis of 7 in cyclohexene leads to a 45% yield of aziridine adduct 10 and a 41% yield of isocyanate 9. Trapping the nitrene does not depress the yield of isocyanate Hence, isocyanate 9 and adduct 10 cannot be derived from the same reactive intermediate. Instead, the isocyanate must be formed from the excited state of the azide, that is, the excited azide (7 ) must partition between the formation of isocyanate and nitrene. 

Addition of IN3 to 1-phenylcyclohexene affords the expected Markovnikov product corresponding to the anfi-mechanism. Although further chemical transformations of the product seemed to be in conflict with the proposed structure, extensive 15N NMR experiments finally convinced the authors that the original structure was correct172,193. Iodination of cyclohexene promoted by silver isocyanate was used to prepare the corresponding l rans-i odocy an ate194. 

Accordingly, the cyclic isocyanate 157, derived from cyclohexene-l-caiboxylic add and cyclohexylisocyanide in acetonitrile under reflux, led, via the hydroindolone 158, to 159 in good yield (Scheme 22). 

Other methods were developed for various anions. Bromides were oxidized with permanganate and the bromine so produced reacted with cyclohexene to form 1,2-dibromocyclohexane [577]. Similarly, iodides were analysed in milk as monoiodoacetone after oxidation with iodate and after reaction of the released iodine with acetone [578]. Pennington [579] utilized the same oxidation reaction for the analysis of iodates the iodine released was analysed as such. Cyanides were chlorinated prior to analysis with chloramine-T and the cyanogen chloride so produced was subjected to GC [580]. Analogously, cyanides and isocyanates form cyanogen bromide with bromine water, which can be analysed by GC [581]. 

The base-catalysed reaction of phenyl isocyanate with the morpholino enamines 339 (R1, R2 = H or Ph) gives uracils 340 (equation 138)167. Dithiouracils 341 (n = 1 or 2) are similarly produced from morpholinocyclopentene or -cyclohexene and aroyl isothiocyanates168. Treatment of the dihydrofurans 342 with aryl isocyanates yields derivatives 343 of furo[2,3-d]pyrimidine by way of transient ureas (equation 139)169. 

Episulfides. Hinshaw reasoned that addition of an alkene to such solutions should give jS-iodothiocyanates in analogy with the reaction of iodine isocyanate (1, 501 2, 223-224 . 3, 161 -16.3) with alkenes. indeed treatment of cyclohexene with iodine thiocyanate gives a /5-iodothiocyanate (2), which on treatment with methanolic... 

Other aminoferrocene precursors are Af-ferrocenyl phthalimide, which can be converted to FC-NH2 by N2H4 H2O in boiling ethanol (82% yield) [16, 44], and ferrocenyl azide, FC-N3, which has been reduced with LiAlH4 (72% yield) (cf. Scheme 5-6) [45]. Ferrocenyl amine, FC-NH2, is generally formed among other products in the thermal or photochemical decomposition of FC-N3 [56] and in the thermolysis of ferrocenyl isocyanate, Fc-NCO [57], in solvents such as cyclohexane, cyclohexene and benzene, probably by reaction of the intermediate nitrene, [Fc-N], with the solvent [56, 57]. The reduction of nitroferrocene, FC-NO2, provides another route to aminoferrocene, FC-NH2 [58 — 61] however, FC-NO2 is not an easily accessible starting material. 

Photolysis of pivaloyl azide in cyclohexene produces 41% isocyanate, 45% JV-pivaloylaziridine (108), T5% of the allylic amide (109), a trace of bi(cyclohex-2-enyl) (110) and some pivalamide (111). 

Cyclohexenyl isocyanate (108), produced from 1-cyclohexenecarboxylic acid (107) and DPPA in situ, reacts with l-(A -pyrrolidinyl)cyclohexene (109) to give the pyridone derivative (110 equation 43). The similar vinyl isocyanate-enamine cyclocondensation presents a general method for the preparation of various pyridone derivatives. 

Apparently, benzoylnitrene is formed in the thermolysis (120 C) of 0,jV-bis(trimethyl-silyljbenzocarboximidicacid and trapped with cyclohexene to give, V-(3-cyclohexenyl)benzamide (10/ ,) together with phenyl isocyanate.168 Benzoylnitrene is apparently also formed by sul-filimine photolysis and trapped with cyclohexene to give A/-benzoyl-7-azabicyclo[4.1.0]heptane (15.6%). 55 ... 

Iodine isocyanate has been used in one step of a stereospecific synthesis of trans-1,2-diaminocyclohexane.6 Iodine isocyanate is added to cyclohexene and the crude... 

Vinylic isocyanates react with enamines such as 1-pyrrolidino-l-cyclohexene under mild conditions to form a new pyridinone ring and simultaneous loss of pyrrolidine [3S40]. Reaction of an ynaminone with phenyl isocyanate in refluxing THF gives good yields of 3-acyl-4-dimethylamino-2-quinolinone [2056]. A perchloroynamine behaves similarly [2838]. 

Butyl-2,3-dihydro[l,2,4]thiadiazolo[4,5-a]benzimidazol-3-one (111 R = Bu") undergoes exchange of the isocyanate moiety (see Section 8.05.10). With DMAD 2,3-dimethoxycarbonyl-thiazolo[3,2-a]benzimidazole (137) is obtained. The reaction with 4-(l-cyclohexen-l-yl)morpholine gives 10a-hydroxy-6a,7,8,9,10,10a-hexahydrobenzimidazo[2,l-ft][l,3]benzothiazole (138) (Scheme... 

Isocyanic acid, methoxymethyl ester. See Methoxymethyl isocyanate Isocyanic acid, methylenedi-4,1-cyclohexene ester Isocyanic acid, methylenedi-4,1-... 

---