1.3.5- Oxathiazole

The isocyanide dichlorides are particularly attractive 1,1-bielectrophiles, and the N-sulfonyl derivative (138) underwent reaction with the iV-hydroxythioamide (137) to give the 1,3,5-oxathiazole derivative (139) (71AP763). Yields varied from 62% for R = Me and were slightly less for R = Ph (57%) and R = p-MeOC6H4 (50%). 

The imino dichloride (430) with the /V-hydroxythioamide (429) gives the 1,3,5-oxathiazole (431) (71AP763). 

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. 

Dichloromethyleneimine sulfonamide 603 with the A-hydroxythioamide 602 gives the 1,3,5-oxathiazole 604 (Scheme 270) <1971AP763>. 

Thiatriazolin-5-imines undergo a variety of cycloaddition reactions with the elimination of Nt. 1,3-Dithiolylium-4-olates undergo cycloaddition reactions, e.g. as in Scheme 36 80AHC(27)i5l). Scheme 37 gives an example of cycloaddition in the oxathiazole series. 

A number of 1,2,3-oxathiazole 5-oxides are prepared from the reaction of thionyl chloride with various ethane derivatives having vicinal oxygen- and nitrogen-containing groups. Reaction of the 2-aminoethanol derivative (146) with SOCI2 gave (147) (see Chapter 4.34). 

Bismuth heterocycles, 1, 539-561 Bismuthiol I metal complexes, 6, 565 IR spectra, 6, 552 ring structure, 6, 561 structure, 6, 557 Bismuthiol II metal complexes, 6, 565 IR spectra, 6, 552 Bisnorisopenicillin, 7, 332, 333 Bisnorpenicillin V, 7, 331 Bis( l,3,4-oxathiazol-2-ones) applications, 6, 945 Bisoxiranes synthesis, 7, 42 Bi(spiroisoxazolines) synthesis, 6, 108 Bi(spirophosphoranes) polytopal rearrangements, 1, 529 reactions, 1, 535 Bispyranones synthesis, 3, 793 a,oj-Bispyranones, alkylene-irradiation, 3, 678... 

Nitrile sulfides (37) have some, admittedly slight, structural affinity with the other nitrogen-sulfur reagents discussed in Section IV. They are unstable reactive intermediates that can be generated by the thermolysis of 1,3,4-oxathiazol-2-ones (38) or of 1,3,4-oxathiazoles (39).41 42 An alternative preparation is by the elimination of 2 moles of hydrogen fluoride from imini-sulfur difluorides (Scheme 5).43 Nitrile sulfides (37) are capable of undergoing... 

Type G syntheses are typified by the 1,3-dipolar cycloaddition reactions of nitrile sulfides with nitriles. Nitrile sulfides are reactive 1,3-dipoles and they are prepared as intermediates by the thermolysis of 5-substituted-l,3,4-oxathiazol-2-ones 102. The use of nitriles as dipolarophiles has resulted in a general method for the synthesis of 3,5-disubstituted-l,2,4-thiadiazoles 103 (Scheme 11). The thermolysis is performed at 190°C with an excess of the nitrile. The yields are moderate, but are satisfactory when aromatic nitrile sulfides interact with electrophilic nitriles. A common side reaction results from the decomposition of the nitrile sulfide to give a nitrile and sulfur. This nitrile then reacts with the nitrile sulfide to yield symmetrical 1,2,4-thiadiazoles <2004HOU277>. Excellent yields have been obtained when tosyl cyanide has been used as the acceptor molecule <1993JHC357>. 

A novel method is reported to convert 1,3,5-oxathiazine-A-oxides 116 into 1,2,4-oxathiazoles 117 under thermal conditions. Lewis acid-promoted reaction of compounds 117 furnishes 1,2,4-thiadiazoles 118 and the final step is a type A synthesis (see Section 5.08.9.2) (Scheme 15) <2004HAC175>. 

Strong acid hydrolysis of 1,2,6-thiadiazine 1,1-dioxides 239 or 240 results in ring contraction to afford the 1,2,5-thiadiazolinone 1,1-dioxides 241 in low yield <1996J(P2)293>. 3-Dialkylamino-2/7-azirines 242 suffer ring expansion with in situ-prepared iV-sulfonylamides 243 and carbamates to give both the 1,2,3-oxathiazoline 244 and the thiadiazoline 1,1-dioxide 245 (Equation 56). The oxathiazole 244 isomerizes quantitatively to the thermodynamically favored thiadiazoline 245 <1996J(P1)1629>. 

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). 

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