Nitrile oxides 1,4,2-oxathiazoles

N-benzyladamantyl-2-imines, and 2-methyleneadamantanes were studied (352, 353). In particular, X-ray single-crystal analysis confirmed the configuration of the oxathiazoline 185, resulting from the favored attack of nitrile oxide on the 5-fluoroadamantane-2-thione. 2-Silyl-substituted oxathiazole 186 was synthesized by the 1,3-dipolar cycloaddition reaction of phenyl triphenylsilyl thioketone with 4-chlorobenzonitrile oxide (354). 

Oxathiazoles are produced from sulfines in 1,3-cycloaddition reactions with nitrones <84CHEC-I(6)934>. With nitrile oxides only those sulfines which have sufficiently strong electron-withdrawing substituents such as CF3 (115) display the desired regioselectivity otherwise 1,3-... 

Also of interest are the cumulative systems of sulfines and of carbon disulfide which react with nitrile oxides to give 5H-1,4,2-oxathiazole S-oxide (220) <77JCS(P1)1468> and 1,4,2-oxathiazol-5-one derivatives (221), respectively <66JOC24l7>. The latter is formed from the primary spiro bis adduct (222) by further decomposition (see also Section 4.14.5.6). 

A cycloreversion mechanism is suggested for the transformation of the nonisolable cycloadduct 90 to the aldehyde 91 and isothiocyanate 92 <1996BCJ719> and for the spiro-1,4,2-oxathiazole intermediates 94 to the dioxothiazoline 95 and the aryl isothiocyanate 92 <2001MOL510>. Both cycloadducts are obtained by cycloaddition reactions of nitrile oxides 88 to thiocarbonyl compounds (Scheme 12). 

Cycloadditions with nitrile oxides occur across the C=S bond both with 1,3,5-oxathiazole-2-thiones (66JOC2417) and l,3,4-dithiazole-2-thiones (Scheme 28) (67BSF2239), the reaction proceeding via an interesting spiro compound which has been isolated in some cases. 

Without additional reagents 1,4,2-Oxathiazoles from nitrile oxides... 

The applicability of thioketones in the synthesis of heterocyclic compounds has been further demonstrated. The Diels-Alder reaction of thiobenzophenone with l,3>5-cycloheptatriene gave the (2 + 4) cycloadduct (101) in 40% yield. Cycloheptatrienethione (92) yielded the (8 + 2) cycloadduct (102) quantitatively by reaction with maleic anhydride, and the bicyclic compound (103) in 65% yield by reaction with dimethyl acetylenedicarboxylate. Compound (103) was considered to be a rearrangement product of the probably primarily formed (8 + 2) cycloadduct intermediate (104). " The in situ addition of nitrile oxides to aromatic thioketones resulted in formation of 1,4,2-oxathiazoles, " whereas 1,4,2-oxathiazolidines were the products in the reactions of some alicyclic thiones with nitrones. The formation of thio-ozonides (1,2,4-trithiolans) by treatment of thioketones with amines or chloramine T was investigated recently. ... 

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