Synthesis of sterically hindered 1-arylpyrrolidines and 1-arylpiperidines by condensation of primary aromatic amines with cyclic ethers or diols

A variety of 1-($\text{o}$-alkylphenyl)- and 1-($\text{o}$-$\text{o}$'-dialkylphenyl)- pyrrolidines and -piperidines were prepared by the gas phase alumina mediated condensation of tetrahydrofuran (THF), tetrahydropyran (THP) or the corresponding diols with primary aromatic amines in fair to high yield. This methodology can also be used for the synthesis of 1-phenylhexahydroazepine from aniline. A mechanistic interpretation of the catalytic action of alumina is presented.     

Concerted cycloaddition of chlorosulfonyl isocyanate to α-pinene stepwise rearrangement of the β-lactam cycloadduct to a γ-lactam

Chlorosulfonyl isocyanate adds to α-pinene in concerted fashion to give the unrearranged N-chlorosulfonyl-β-lactam 2 (75%). Thermolysis of cycloadduct 2 affords the rearranged N-chlorosulfonyl-γ-lactam 6 (60%) via a sequence of transient carbonium ions (45). Reductive hydrolysis of 2 and 6 gave, respectively, the NH-β-lactam 3 (70%) and the NH-γ-lactam 7 (70%). Proof of structure of the rearranged γ-lactams 6 and 7 are provided, respectively, by X-ray crystallographic analysis and the application of the Eu(dpm)₃ NMR shift reagent.