Synthesis of a novel diene from a cyclobutane precursor: an entry to 2,9-disubstituted [2]diadamantanes

Synthesis of 1,2-Disubstituted Adamantane Derivatives by Construction of the Adamantane Framework

This review summarizes achievements in the synthesis of 1,2-disubstituted adamantane derivatives by the construction of the tricyclic framework either by total synthesis or by ring expansion/contraction reactions of corresponding adamantane homologues. It is intended to complement reviews focusing on the preparation of 1,2-disubstituted derivatives by C-H functionalization methods.

Short Access to Belt Compounds with Spatially Close C=C Bonds and Their Transannular Reactions

Two domino Diels-Alder adducts were obtained from 3,7-bis(cyclopenta-2,4-dien-1-ylidene)-cis-bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N-methylmaleimide under microwave irradiation. From the first adduct, a C20H24 diene with C2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X-ray diffraction analysis upon irradiation of the diene crystal. New six-membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N-type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack.

Tri-cyclo-[3.3.1.0(3,7)]nonane-3,7-diyl bis-(4-methyl-benzene-sulfonate)

The title compound, C23H26O6S2 was synthesized by esterification of tri-cyclo-[3.3.1.0(3,7)]nonane-3,7-diol with p-toluene-sulfonyl chloride. The mol-ecule has symmetry 2 and is situated on site 4e. The C-C bond length between the quartenary C atoms is 1.598 (2) Å, which is considerably longer than other C-C bonds in the mol-ecule. There are C-H⋯O inter-actions present in the structure. As a consequence, the packing of the molecule (viewed along [100]) appears as chains where the molecules run parallel, but each chain has the opposite direction to the neighboring ones.