Elektrophile Additionen an das Bicyclo[1.1.0]butan‐System von 1‐Phenyl‐ und 1‐(4‐Anisyl)tricyclo[4.1.0.02,7]heptan: Säure‐katalysierte Reaktionen mit Wasser und Methanol, Anlagerung von Essigsäure und Oxymercurierung

Abstract

Electrophilic Additions to the Bicyclo[1.1.0]butane System of 1‐Phenyl‐ and 1‐(4‐Anisyl)tricyclo[4.1.0.02,7]heptane: Acid‐Catalyzed Reactions with Water and Methanol, Addition of Acetic Acid, and Oxymerucuration1‐(4‐Anisyl)tricyclo[4.1.0.02,7]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.