Other miscellaneous heterocyclic derivatives

Ethylene oxide or oxirane is the simplest a-epoxide (for reviews see Refs. I00-I03). Epoxides or oxirane derivatives may generally be formed by treatment of ethylenic compounds or ds-diols with peracids [104-106]. Episul-phide analogues can also be formed [107]. Epoxides can be analysed by TLC. GC or MS. 

The monounsaturated fatty add ester (3/il) is mixed with peracetic add (150/il) and allowed to stand for 2—3 h at room temperature. For dienes, twice the amount of peracetic add and at least twice the reaction time are needed. Samples may be analysed directly or neutralized with soldium bicarbonate and extracted with hexane for subsequent GC analysis [108,109.  

The diol (1 mmol) and dry pyridine (150 /il) were dissolved in alcohol-free chloroform (1 ml), and phosgene was gently bubbled through the solution for 1 h at 0 °C and then for a further 2-3 h at room temperature. The organic solution was extracted with an equal volume of water several times until neutral, then dried over anhydrous calcium sulphate [110, 111]. 

The carbonate and thiocaibonate derivatives used in the carbohydrate field have been reviewed 112]. The cyclic carbonates are sensitive to alkali and stable to add hydrolysis, and in these respects are complementary to the cydic isopropylidene acetals. Cydic carborrates may be made from sugars by the action of chloroformate esters. The original phosgerre method is also applicable, either directly or in a solvent. The solvent usually used is toluene, or a reaction-promoting solvent such as pyridine or quinoline may be used. 

The fivanose ring seems preferred, so that for example D-mannopyranose yields the D-manno furanose-2.3-caibonate [113], Cyclization between frans-hydroxyl groups is not usual. 

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A few other miscellaneous cyclizations are worthy of mention. o-Substituted benzene derivatives of general structure 382 (X = O, S or NH) undergo oxidative cyclization on irradiation to give the corresponding heterocyclic system (383),402 Similar behavior is exhibited by a thioamide [Eq. (102)]. Nonoxidative photoeyclization... 

Miscellaneous. The azide is used for the preparation of other heterocyclic compounds. Typical examples are the formations of disilaaziridine (eq 9) and i -triazine (eq 10) derivatives. 

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