Elektrophile Additionen an das Bicyclo[1.1.0]butan‐System von 1‐Phenyl‐ und 1‐(4‐Anisyl)tricyclo[4.1.0.0 2,7 ]heptan: Säure‐katalysierte Reaktionen mit Wasser und Methanol, Anlagerung von Essigsäure und Oxymercurierung

Electrophilic Additions to the Bicyclo[1.1.0]butane System of 1‐Phenyl‐ and 1‐(4‐Anisyl)tricyclo[4.1.0.0 2,7 ]heptane: Acid‐Catalyzed Reactions with Water and Methanol, Addition of Acetic Acid, and Oxymerucuration 1‐(4‐Anisyl)tricyclo[4.1.0.0 2,7 ]heptane ( 37 ) was prepared from 1‐(4‐anisyl)cyclohexene, tetrabromomethane, and methyllithium in a one‐pot reaction. Starting from 37 and the analogous phenyl compound 19 , the oxymercuration/demercuration sequence provided the exo ‐6‐aryl‐ endo ‐6‐norpinanols 30a and 20a , respectively. By reaction with triphenyl‐stannane, the bromo compound 27a was converted into endo ‐6‐phenyl‐ exo ‐6‐norpinanol 28a . Treatment of 19 with aqueous sulfuric acid led to a mixture of the alcohols 20a–25a . Mixtures of a very similar composition were obtained on hydrolysis of the 3,5‐dinitrobenzoates 20b and 28b of 20a and 28a in 80% aqueous acetone. Kinetic measurements revealed the same rate for the hydrolysis of 20b and 28b . The proof of the presence of 20a among the products of the reactions of 19, 20b , and 28b showed the intermediacy of an unrearranged cation, to which the classical structure 16 is ascribed. That acetic acid is too weak a nucleophile to intercept 16 follows from the structure of the adducts to 19 . All of them ( 21b, 22b, 25b, 26b ) have rearranged skeletons. In contrast, the stronger nucleophile methanol trapped 16 more efficiently than water to give the diastereomeric 6‐norpinyl methyl ethers 20d and 28d . The reaction of 37 with acetic acid and 10 −4 M hydrochloric acid as well as the hydrolysis the 3,5‐dinitrobenzoate 30c of 30a produced mainly the diastereomeric 6‐norpinyl acetates 30b and 31b and 6‐norpinanols 30a and 31a , respectively. Whereas the protonation of 19 and 37 gives the classical cations 16 and 17 , respectively, the oxymercuration of these substrates results in the generation of the nonclassical cations 44 and 46 . This was concluded from the configuration of the demercuration products 20a and 30a and the absence of the diastereomers 28a and 31a .