Intramolecular Migration of Bulky Substituents in the Solid State: Vinylogous Pinacol Rearrangements Induced Thermally and by Acid Catalysis

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• 作者：Ryo Sekiya ; Kazuhiko Kiyo-oka ; Tatsuro Imakubo ; and Keiji Kobayashi
• 刊名：Journal of the American Chemical Society
• 出版年：2000
• 出版时间：October 25, 2000
• 年：2000
• 卷：122
• 期：42
• 页码：10282 - 10288
• 全文大小：102K
• 年卷期：v.122,no.42(October 25, 2000)
• ISSN：1520-5126

文摘

A vinylogous pinacol rearrangement, involving an intramolecular 1,4-migration of the bulkythienothienyl substituent and a marked change of the crystal structure, was thermally induced in the solid statefor thienothienyl-substituted 9,10-dihydroxy-9,10-dihydroanthracenes, 1 and 3~8. When heated over 180 to~240 C, these crystals were transformed quantitatively, accompanying dehydration, to crystals of the anthronederivatives without wetting or melting. Diol 8, which bears two isomeric thienothiophene rings, afforded onlya single anthrone product. Compounds 1 and 8 formed a mixed crystal and its thermally induced reactionyielded two anthrone products that were attributable to intramolecular migration but afforded no anthronederivative having the two substituents possible for the intermolecular combination. These results, along withthe X-ray crystal structure of the mixed crystal, demonstrate that the rearrangement in the solid state proceedsintramolecularly. The 1,4-pinacol type rearrangements were also induced, along with the cis-trans isomerization,by cogrinding the diols with p-toluenesulfonic acid in a mortar at room temperature. The intramolecularity ofthe rearrangement was again proved by the use of the mixed crystal. The intervention of the carbocation in thesolid-state grinding was ascertained by the UV/vis spectra. The time courses of the product distributions showeddiscrete profiles between the trans and cis diols, 1 and 3, respectively; for the trans diol 1, fast isomerizationto the cis isomer and consecutive formation of the rearranged product via the cis isomer were observed. Onthe basis of these observations, the solid-state 1,4-rearrangement was deduced to occur preferentially via thecis configuration of the dihydroxy groups.