Dihydro-1,3-oxathiins, synthesis

Further, a 1,2-oxathiane 2,2-dioxide derivative was obtained as a by-product (15-25%) in the enantioselective synthesis of Oasomycin A <2007AG545> all efforts to suppress this side reaction were not successful, and the reaction products of the hexafluorobutadiene sulfotrioxidation (among the main products a 4,5-dihydro-l,2-oxathiin 2,2-dioxide derivative) were identified by F NMR spectroscopy <2007RJA424>. 

Optically pure 1,3-oxathiins have been used as chiral auxiliaries for the synthesis of (E)-monoaryl epoxides (95JOC3494) and (5-substituted ketones (95SL501), whilst the desulfurisation of some dihydro-1,4-oxathiins affords E-alkyl vinyl ethers (95SL1274). 

A cyanosulfine [242] and an oxosulfine [162] were trapped with 2,3-dimethyl-1,3-butadiene (Table 6, entries 2 and 3). Capozzi and his group have extended their phthalimido-sulfenyl chemistry to the synthesis of a-oxosulfines, and have observed a dichotomic behaviour towards cycloaddition. With 1,3-dienes, these sulfines act [243, 244] as dienophiles through their C=S bond (Table 6, entry 4) to afford dihydro-2H-thiapyran S-oxides. With alkenes (Table 7), such as 2,3-dimethyl-2-butene (entry 1) or vinyl-ethers (entry 2), they behave as dienes to give dihydro-1,4-oxathiin S-oxides [243-245]. 

Dioxins, 1,4-oxathiins, and 1,4-dithiins are commonly prepared by elimination reactions from saturated analogues (see Section 4.3.4.1.4). A convenient synthesis of 2,3-dihydro-1,4-dioxins (e.g., 442) starts from propargyl chloride and 1,2-ethanediol (Scheme 206) . Another approach to substituted 2,3-dihydro-... 

The most widely used fungicide of the carboxamide group, carboxin (9), contains an oxathiin ring. Its composition is 5,6-dihydro-2-methyl-l,4-oxathiin-3-carboxanilide (Von Schmeling and Kulka, 1966). Its synthesis starts with acetoacetanilide (7), which with sulfuryl chloride gives 2-chloro-3-oxobutyranilide... 

Dihydro-l,4-benzodithiines and -oxathiines. A remarkable one-pot synthesis of these heterocycles from cyclohexanones and ethanedithiol or 2-mercapto-ethanol is mediated by NBS at 0°C. 

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