94526-06-4Relevant articles and documents
Preparation, Pyrolysis, and Photolysis of Three Sterically Crowded Alkenes, 3,3,3',3',5,5,5',5'-Octamethyl-3,3',5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) 2,2,4,4-Tetramethyl-3-(3,3,5,5-tetramethyl-3,5-dihydro-4H-pyrazol-4-ylidene)-thietane 1,1-Dioxide and 2,2,2',2',4,4,4',4'-Octameth...
Bushby, Richard J.,Mann, Stephen,Jesudason, Malini, V.
, p. 2457 - 2464 (2007/10/02)
Photolysis and pyrolysis of the title compounds involve a stepwise elimination of nitrogen and/or sulphur dioxide and reactions which can be interpreted in terms of a series of trimethylenemethane (TMM) biradical intermediates.However, the photosensitised photolysis of the bi(pyrazolylidene) (11) give products indicative of an elimination of both nitrogens and the generation of a tetramethylene-ethane (TME) biradical intermediate.New synthesis of a number of highly sterically crowded alkenes including 2,2,4,4-tetramethyl-3-(3,3,5,5-tetramethyl-3,4-dihydro-4H-pyrazol-4-ylidene)thietane 1,1-dioxide (12) and 2,2,2',2',4,4,4',4'-octamethyl-3,3'-bithietanylidene 1,1,1',1'-tetraoxide (13), are described.Flash vacuum pyrolysis (f.v.p) of 3,3,3',3',5,5,5',5'-octamethyl-3,3'-5,5'-tetrahydro-4,4'-bi(4H-pyrazolylidene) (11) at 400 deg C gives 3,3,5,5-tetramethyl-4-(2,2,3,3-tetramethylcyclopropylidene)-3,5-dihydro-4H-pyrazole (21), at ca. 400 deg C 1-isopropylidene-2,2,4,4,5,5-hexamethylspiropentane (22), and at ca. 580 deg C a ca. 5:1 mixture of 4-isopropyl-3-isopropylidene-2,5-dimethylhexa-1,4-diene (23) and 2-(2,3-dimethylbut-1-en-3-yl)-1-isopropyl-3,3-dimethylcyclopropene (27).Above 700 deg C a complex mixture of aromatic products and low molecular weight hydrocarbons is produced which includes ethane, ethylene, propene, isobutane, and isobutene, p-xylene, o-cumene and probably m-cumene, and 2,5-dimethylisopropylbenzene.F.v.p. of the dihydropyrazole sulphone (12) gives initially 2,2,4,4-tetramethyl-3-(2,2,3,3,-tetramethylcyclopropylidene)thietane 1,1-dioxide (41) and at higher temperatures similar mixtures to those obtained from the bipyrazolylidene (11).Similar results were also obtained for the f.v.p. of the bis-sulphone (13).Photolysis of the bipyrazolylidene (11) gave initially the dihydropyrazole (21) and then a 48:52 mixture of the spiro compound (22) and 2,2,2',2',3,3,3',3'-octamethylbicyclopropylidene (42).Photolysis of the dihydropyrazole sulphone (12) gave 2,2,4,4-tetramethyl-3-(2,2,3,3-tetramethylcyclopropylidene)thietane 1,1-dioxide (41).Benzophenone-sensitised photolysis of the bipyrazolylidene (11) gave 1,2-di-isopropylidene-3,3,4,4-tetramethylcyclobutane (32).
