Dithiolane, decomposition

The reaction with sulfides occurs efficiently only when the resulting carbon-centered radicals are further stabilized by a a-heteroatom. Indeed, (TMSfsSiH can induce the efficient radical chain monoreduction of 1,3-dithiolane, 1,3-dithiane, 1,3-oxathiolane, 1,3-oxathiolanone, and 1,3-thiazolidine derivatives. Three examples are outlined in Reaction (12). The reaction of benzothiazole sulfenamide with (TMS)3SiH, initiated by the decomposition of AIBN at 76 °C, is an efficient chain process producing the corresponding dialkylamine quantitatively. However, the mechanism of this chain reaction is complex as it is also an example of a degenerate-branched chain process. 

The products of the thermolysis of 3-phenyl-5-(arylamino)-l,2,4-oxadiazoles and thiazoles have been accounted for by a radical mechanism.266 Flash vacuum pyrolysis of 1,3-dithiolane-1-oxides has led to thiocarbonyl compounds, but the transformation is not general.267 hi an ongoing study of silacyclobutane pyrolysis, CASSF(4,4), MR-CI and CASSCF(4,4)+MP2 calculations using the 3-21G and 6-31G basis sets have modelled the reaction between silenes and ethylene, suggesting a cyclic transition state from which silacyclobutane or a trcins-biradical are formed.268 An AMI study of the thermolysis of 1,3,3-trinitroazacyclobutane and its derivatives has identified gem-dinitro C—N bond homolysis as the initial reaction.269 Similar AMI analysis has determined the activation energy of die formation of NCh from methyl nitrate.270 Thermal decomposition of nitromethane in a shock tube (1050-1400 K, 0.2-40 atm) was studied spectrophotometrically, allowing determination of rate constants.271... 

Rhodium-catalysed decomposition of methyl diazoacetate (1.2 equiv.) in the presence of 1,3-dithiolane yields mainly dithiane (31) as a mixture of diastereoisomers.34 Ring-expanded product (32) and ring-opened products (33) arising from a second condensation of the carbene are also isolated, albeit in low yield. Similar reactivity is observed with 1,3-oxathiolane. 

The 1,3-dipolar cycloaddition of the carbonyl ylide (31) to the aldimine (32) produces the adduct (33), which has been used to synthesize the taxol C(13) side-chain (34), which is known to be required for the antitumour activity of taxol (Scheme 9).35 The dirhodium tetraacetate-catalysed decomposition of l-diazo-5-phenylpentane-2,5-dione (35) yields the carbonyl ylide (36), which cycloadds to methylenecyclopropanes (37) to produce spirocyclopropanated 8-oxabicyclo[3.2.1]octan-2-ones [(38)-(40)] in 6-75% yields (Scheme 10).36 The 1,3-dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides with thiobenzophenone produce both regioisomeric 1,3-dithiolanes as expected. However, in the case of highly sterically hindered thiocarbonyl ylides, methylene transfer leads to the formation of 4,4,5,5-tetraphenyl-l,3-dithiolane.37,38... 

Though the anion of dithiolane decomposes as described in the chapter and cannot be used as a d1 reagent, the example shown here works well without any decomposition. Explain and comment on the regioselectivity of the reaction. Anions of dithianes are notorious for preferring direct to conjugate addition. 

DSP710 CAS 71108-06-0 HR 3 5,5-DIMETHYL-2-((1-METHYLETHYL). IMINO)1,3-DITHiOLAN-4-ONE, o- (METHYL( TRICHLOROMETHYL)THI 0)AMINO)CARBONYL)OXIME mf CuHi6Cl3N302S3 mw 424.83 SAFETY PROFILE A poison by ingestion. When heated to decomposition it emits toxic vapors of NOx, SOx, and CL. 

Rhodium(ll)-catalyzed decomposition of diazoketones 324 bearing the 1,3-dithiolane moiety, in the presence of benzaldehyde and ClTi(Or-Pr)3, afforded a mixture of the ring-enlarged enone 325 in 22% yield and the ring-transformed thiophenone 326 in 55% yield (Equation 34) <2004JOC2899>. 

The dipolar 1,3-cycloaddition reaction of thiocarbonyl ylides to thiones can be a source of 1,3-dithiolanes. Its regioselectivity depends on the nature of substituents in the substrates. Thus, the. J-methylide 589, generated in situ by thermal decomposition of the corresponding l,5-dihydro-l,3,4-thiadiazoles, was reacted with the trithiocarbonate 588 to give a labile 4,4,5,5-tettasubstituted-l,3-dithiolane 590, which easily isomerized to an open-chain compound 591 in the presence of acids in solution (Scheme 84) <2000EJ01695>. 

The decomposition of the dithiolane anion is a reverse cycloaddition and occurs because t stabilization given to the anion by two sulfur atoms is not very great. This anion is an enolate as wej so it is much more stable. Conjugate addition is preferred (p. 751) with more stable enolates ar this anion is an enolate additionally stabilized by two sulfur atoms. The three groups (ester and v S atoms) combine to make a stable anion good at conjugate additions. 

Cyclic Disulphides and Cyclic Diselenides.—Formation. No fundamentally new methods of synthesis of this class of compounds have been reported in the past two years. For l,2>dithiolan the oxidation of l,3>dithiols remains a favoured method, the use of iodine in the presence of triethylamine leading smoothly to 1,2-dithiolans without attendant polymerization. cis- and tra/ -l,2-Dithiolan-3,5-dicarboxylic acids were prepared from a diastereo-isomeric mixture of dimethyl 2,4-dibromoglutarates by sequential treatment with potassium thioacetate and potassium hydroxide in the presence of iodine,and jyn-2,3-dithiabicyclo[3,2,l]octan-8-ol was formed from 2,6-dibromocyclohexanone by successive treatment with potassium thiocyanate, lithium aluminium hydride, and iodine. The stereoselective formation of the less thermodynamically stable alcohol in this case was attributed partly to the formation of chelates with sulphur-aluminium bonds. 2,2-Dimethyl-l,3-dibromopropane was converted into 4,4-dimethyl-l,2-diselenolan on treatment with potassium selenocyanate at 175 °C, but at 140 °C the product was 3,3-dimethylselenetan. Reductive debenzylation of 2-alkylamino-l,3-bis(benzylthio)propanes with lithium in liquid ammonia and oxidation of the resultant dithiols with air afforded 4-dialkylamino-l,2-dithiolans, whilst treatment of a-bromomethyl-chalcone with sodium hydrosulphide gave, as minor product, trans-3 phenyl-4-benzoyl-l,2-dithiolan. Among the many products of thermal decomposition of /ra/ -2,4-diphenylthietan was l,4,5,7-tetraphenyl-2,3-dithiabicyclo [2,2,2]octane. ... 

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