Control of cage opening reactions in the 1,3-bishomocubane and homocubane systems |
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| Institution: | 1. Novosibirsk State University, Pirogova, 2, Novosibirsk 630090, Russia;2. Heilongjiang University, Xue Fu Road, No. 74, Nan-gang, Harbin 150080, PR China;3. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Pr. Akademika Lavrentieva, 5, Novosibirsk 630090, Russia;1. Departamento de Física Aplicada, CINVESTAV Unidad Mérida, Mérida, Yucatán 97310, Mexico;2. Department of Earth System Science, Stanford University, Stanford, CA 94305, USA;3. Escuela de Ingeniería, Universidad Marista de Mérida, Mérida, Yucatán 97300, Mexico |
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| Abstract: | The synthesis and base-induced cage opening of 5-fucctionalized homocubyl alcohols 22 (R is some protective group) is described. In a first approach, the synthesis of 22 has been attempted starting from tricyclic enol 14 and involving the Favorskii cage contraction of l,3-bishomocubanones 24. Unexpectedly, 4-methoxypentacyclo 5.3.0.02,5.03,9.04,8]decan-6-ones 24b and 29 undergo a facile add-catalyzed cage fragmentation to give tricyclo5.3.0.02,5]decene diones 28a and b, respectively. The Favorskii cage contraction of 24 to homocubane carboxylic add 25c has been accomplished for the MEM-protected 24c, albeit in low yield. With silver cations under basic conditions, 24b and c undergo an unusual oxidative cage fission reaction leading to tetracyclo4.3.0.02,4.03,8]nonan-5-one 7-carboxylic acids 40 and 41. An efficient route to 4-bromohomocubyl acetate 48 has finally been accomplished starting from 4,5-dibromo-l,3-bishomocubanone 43. Base-induced homoketonization of 48 is essentially directed by the 5-bromine atom and a regioapedfic cleavage of the central C4–C5 bond is observed, producing, in a stereospecific manner, 10-oxapeatacyclo 5.3.0.02,6.03,9.04,8]decane 51. |
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