An alternate route to substituted 6,7-dihydro 5H-dibenz[c,e]azepines from allylbenzamides derived from the Morita–Baylis–Hillman adducts

Convenient approach to polyoxygenated dibenzo[c,e]pyrrolo[1,2-a]azepines from donor–acceptor cyclopropanes

A convenient approach to polyoxygenated tetrahydrodibenzo[c,e]pyrrolo[1,2-a]azepines from the donor–acceptor cyclopropanes has been developed.

Axial stereocontrol in tropos dibenz[c,e]azepines: the individual and cooperative effects of alkyl substituents

6,7-Dihydro-5H-dibenz[c,e]azepines, a class of secondary amine incorporating a centre-axis chirality relay, can be prepared from N-(2-bromobenzyl)-N-(1-arylalkyl)methanesulfonamides via Pd-catalysed intramolecular direct arylation, and methylated at C(7) via the 5,7-trans diastereoselective addition of methylmagnesium bromide to the derived N-benzylazepinium tetraphenylborate. Using these methods, the 4,5-dimethylated and 4,5,7-trimethylated homologues 13 and 14 were obtained and shown by ¹H NMR spectroscopy to be axially biased in opposite senses, as defined by the respective pseudoaxial or pseudoequatorial orientation of the 5-substituent in the preferred conformers, while retaining their tropos nature (the Arrhenius activation energy, E_A, for the conformational exchange process in 14 was estimated to be 57 kJ mol^-1 using 2D-EXSY NMR spectroscopy at 233-248 K). These results serve to illustrate how substituent effects might be exploited in new designs of bridged biaryl ligand in which tropos dynamics operate in combination with a pre-existing axial stereochemical bias.

Total Synthesis of (±)-Allocolchicine and Its Analogues Using Co-Catalyzed Alkyne [2 + 2 + 2]-Cyclotrimerization

The total synthesis of (±)-allocolchicine has been completed by employing cobalt-catalyzed alkyne [2 + 2 + 2]-cyclotrimerization as the key reaction. The essential diyne has been synthesized from easily available 3,4,5-trimethoxybenzaldehyde following simple chemical transformations. In general, the cycloaddition gave a mixture of C(9) and C(10) isomers thus allowing the synthesis of both allocolchicine and its C(10)-carboxylate. Because this cycloaddition was employed at the penultimate stage, it allowed the synthesis of various analogues having the diverse functionality at C(9) and/or C(10) of ring C.