| Summary: | A discussion of hydride shifts of an order greater than 1,2 is followed by some illustrative examples. Ethyl cyclooctylidene acetate and cyclooctylidene methyl ketone were reacted with boron trifluoride etherate, but the only reaction observed was isomerisation to cyclooct-l-ene derivatives. Sulphuric, or toluene p-sulphonic, acids treatment of either double bond isomer of the ester gave 1-oxabicyclo[6.3.0]undecan-2-one. 8-(p-Methoxyphenyl)-6,6-dimethyloct-3-en-2-one underwent a 1,5 hydride shift upon treatment with perchloric acid to give 2-(p-methoxy-phenyl)-4,4-dimethylcyclohexyl methyl ketone. Treatment of ethyl 7-(p-methoxyphenyl)-5,5-dimethylhept-2-enoate with hydrobromic acid/ acetic acid gave only 7-(p-hydroxyphenyl)-5,5-dimethylhept-2-enoic acid. Attempts to induce a 1,4 hydride shift by acid treatment of 7-(p-methoxyphenyl)hept-3-en-2-one or 7,7-bis-(p-methoxyphenyl)hept-3-en-2-one were unsuccessful. Wolff-Kishner reduction of 4-(p-anisoyl)-3,3-dimethylbutyric acid, followed by methylation with dimethyl sulphate, gave 2,4,5,6-tetrahydro-7- -(p-methoxyphenyl)-2,5,5-trimethyl-1,2-diazepin-3-one. Transannular ?-reactions and interactions in alicyclic systems are reviewed. Ethyl (cyclooct-3-enylidene) acetate reacted with boron trifluoride etherate in benzene to give an inseparable mixture of products, whereas ethyl (cyclooct-4-enylidene) acetate and cyclooct-4-enylidene methyl ketone, under the same conditions, gave 1-phenylbicyclo[3.3.1]nonane-9-carboxylic acid and its ethyl ester, and 9-acetyl-1-phenylbicyclo[3.3.1]nonane, respectively. The structure of the ester product was proved by degradation to 1-phenylbicyclo[3.3.1]nonan-9-one, whose identity was proved by rational synthesis. An authentic sample of 9-acetyl-1- -phenylbicyclo[3.3.1]nonane was prepared from 1-phenylbicyclo[3.3.1]-nonane-9-carboxylic acid. Treatment of ethyl (cyclooct-4-enylidene) acetate with boron trifluoride etherate alone, followed by esterification, gave 9-carboethoxybicyclo[3.3.1]nonane; with toluene as co-solvent l-(p-tolyl)bicyclo[3.3.1]nonane-9-carboxylic acid and its ethyl ester were produced. Nitrobenzene as a co-solvent in this reaction gave no discernible products. Under the usual reaction conditions dimethyl 3,3-(cyclooct-4'-enyl)glutarate and ethyl 2-(cyclooct-4'-enyl)-2-phenyl acetate did not react. Possible mechanisms for this reaction are discussed. A similar reaction was observed when 7-exo-methylene- bicyclo[3.3.1]non-3-enylidene acetate was treated with boron trifluoride etherate in benzene, but the products were not fully characterised.
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