Tosylhydrazones special

A few special syntheses of thiirane derivatives from four-membered sulfur heterocycles are known. Methylenethiiranes are derived by thermolysis of the tosylhydrazones of thietan-3-ones (Scheme 143) (81TL4815), and 2,2,3,3-tetrakis(trifluoromethyl)thiirane is obtained by thermolysis of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane 1,1-dioxide with loss of sulfur dioxide. 2,2,3,3-Tetrakis(trifluoromethyl)thiirane 1,1-dioxide is obtained in low yield by heating a mixture of 3,3-bis(trifluoromethyl)-l,2,4-oxadithietane 2,2,4,4-tetroxide and bis(trifluoromethyl)ketene. The mono-episulfide of norbornadiene is obtained from thietane derivative (65 Scheme 144) (73JOC649). 

A special case is the reaction of the tosylhydrazone 7 of cyclopropane carbalde-hyde. It conveniently gives access to bicyclobutane" 8 ... 

In keto steroids the reductions were also achieved by electrolysis in 10% sulfuric acid and dioxane using a divided cell with lead electrodes (yields 85-97%) [862], hy specially activated zinc dust in anhydrous solvent (ether or acetic anhydride saturated with hydrogen chloride) (yields 50-87%) [155, 86J], and by the above mentioned reduction of tosylhydrazones with sodium borohydride (yields 60-75%) [811]. 

Various ot,p y,5-unsaturated 1,3-dipoles are known to undergo 1,7-cyclization by a 871-electrocyclization process (329,330), and the corresponding diazo compounds behave similarly. 5-Diazopenta-l,3-diene derivatives such as 285 (Scheme 8.70), generated in situ by thermolysis of the corresponding tosylhydrazone sodium salts, cyclize to form 1,2-diazepines (286) (331). Sharp and co-workers studied the mechanism, scope, and limitations of this transformation. It was found that cis-substitution about the y,8-double bond prevents the 1,7-cyclization and directs the system toward 1,5-cyclization (332,333) (i.e., formation of a 3//-pyrazole), and that the ot,(3-double bond can be part of a phenyl ring (334). In special cases, the y,8-double bond can be incorporated as part of an aromatic [287 288 (335)] or 2- or 3-thienyl ring as well (336). 

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