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Solid-State Photodimerization of Methyl ( RS )-1-Phenyl-2-piperidinoethyl ( RS )-1,4-Dihydro-2,6-dimethyl-4-(2-thiazolyl)pyridine-3,5-dicarboxylate Hydrochloride Controlled by the Buffer Zone

1998; Oxford University Press; Volume: 71; Issue: 2 Linguagem: Inglês

10.1246/bcsj.71.321

1348-0634

Nobuhiro Marubayashi, Takayuki Ogawa, Noriaki Hirayama,

Structural and Chemical Analysis of Organic and Inorganic Compounds

Abstract The solid-state photodimerization of three polymorphic crystal forms (forms I, II, and III) of a bulky olefin, methyl (RS)-1-phenyl-2-piperidinoethyl (RS)-1,4-dihydro-2,6-dimethyl-4-(2-thiazolyl)pyridine-3,5-dicarboxylate hydrochloride, was studied. Forms I and II are anhydrous crystals and form III is an isomorphous hydrate of form II. X-Ray analyses of these forms showed that forms II and III have the same geometrical characteristics suggesting high susceptibility to photodimerization according to the well-known topochemical rule. Although UV irradiation of from II affords a photodimer, 4a,8a-dimethoxycarbonyl-2,4b,6,8b-tetramethyl-3-[(RS)-1-phenyl-2-piperidinoethoxycarbonyl]-7-[(SR)-1-phenyl-2-piperidinoethoxycarbonyl]-(4RS,8SR)-4,8-di(2-thiazolyl)-1,4,4a,4b,5,8,8a,8b-octahydro-cis-transoid-4a,4b-cis-cyclobuta[1,2-b : 3,4-b′]dipyridine, in high yield, the photolysis of form III proceeds much more slowly than that of form II. A detailed inspection of the crystal structures revealed that there is a space to afford the mobility of molecules for dimerization in form II, whereas the space is occupied by the incorporated water molecule in form III. We have previously proposed that a buffer zone, which is a space in the crystal structure, controls the photodimerization of bulky olefins. The present study demonstrates that the buffer zone is an essential controlling factor for the solid-state photodimerization of bulky olefins.