Palladium-Catalyzed Regiocontrolled Domino Synthesis of N-Sulfonyl Dihydrophenanthridines and Dihydrodibenzo[c,e]azepines: Control over the Formation of Biaryl Sultams in the Intramolecular Direct Arylation

Abstract

A palladium-catalyzed domino N-benzylation/intramolecular direct arylation involving sulfonanilides and 2-bromobenzyl bromides has been developed for the first time, providing a workable access to N-sulfonyl dihydrophenanthridines in good to excellent yields. Under the optimized conditions, the formation of 5,6-dihydrophenanthridines was largely controlled over the formation of biaryl sultams containing a seven member ring. The optimized condition was found extendable to the regiocontrolled domino formation of N-sulfonyl-6,7-dihydro-5H-dibenzo[c,e]azepines over the biaryl sultam formation. Using an appropriate substrate, a biaryl sultam has been obtained exclusively.

Palladium‐Catalyzed Regio‐ and Chemo­selective Reactions of 2‐Bromobenzyl Bromides: Expanding the Scope for the Synthesis of Biaryls Fused to a Seven‐Membered Sultam

“…[8] Recently, our group also developed a palladium-catalyzed intramolecular oxidative coupling strategy that involves C(sp 2 )-H double bonds for the synthesis of five-, [9] six-, [10] and seven-membered [10] (hetero)biaryl sultams by using AgOAc as a mild oxidant. Subsequently, Youn et al reported the competitive formation of seven-membered biaryl sultams in the ortho-C-H hydroxylation of N-sulfonylbenzylamines by using K 2 S 2 O 8 as a strong oxidant.…”

Sultams: Recent Syntheses and Applications

“…In 2014, Laha and co‐workers synthesized the biaryl sultams 8.3 from sulfonamide derivatives 8.1 and 2‐bromobenzyl bromide derivatives 8.2 through Pd‐catalyzed regiocontrolled domino N ‐benzylation along with direct arylation (Scheme ) …”

Synthesis of phenanthridine and phenanthridinone derivatives based on Pd‐catalyzed C–H activation

“…Laha research group found that the formation of biaryl sultam could be avoided completely by using N‐Ms anilines. Finally, the synthesis of phenanthridines was achieved by deprotecting dihydrophenantridines with TBAF in acetonitrile reflux …”