CYCLOADDITIONS WITH ALKOXYNITRILE OXIDES, RO-C-EQUIVALENT-TO-N-O-, (ALKYL CYANATE N-OXIDES)()

Alkyl formhydroximates have been synthesized by reacting alkyl orthoes ters with hydrogen sulfide followed by treatment of the alkyl thioform ate formed with hydroxylamine. Chlorination of alkyl formhydroximates with N-chlorosuccinimide gives alkyl chloroformhydroximates and dehydr ochlorination with base generated alkoxynitrile oxides (alkyl cyanate N-oxides), which efficiently undergo cycloaddition to olefins or acety lenes to give 3-alkoxyisoxazolines or 3-alkoxyisoxazoles, respectively . These compounds are masked beta-hydroxy- and beta-keto-esters. Reduc tive cleavage of the ring was performed by hydrogenation over Raney-Ni or with Ti3+ salts. The reaction thus constitutes a novel hydroxycarb oxylation. DL-N-Boc-gamma-amino-beta-hydroxybutyrates (Gabob), mevalon ic acid, citromalic acid, malic acid derivatives and N-methyl-N-hydrox ythioformamide (thioformin) have been synthesized. N,N-Dimethyl-N'-hyd roxychloroformamidine (N,N-dimethylaminochloroform oxime) was not form ed by chlorination of N,N-dimethyl-N'-hydroxyformamidine. The nitrile oxide cycloaddition to cycloheptatriene was investigated. The [6 + 4] cycloaddition mode was not observed but three isomeric [4 + 2] cycload dition products were isolated and structurally determined.