Novel Extensions of the tert-Amino Effect: Formation of Phenanthridines and Diarene-Fused Azocines from ortho-ortho′-Functionalized Biaryls

Abstract

Novel Extensions of the tert-Amino Effect: Formation of Phenanthridines and Diarene-Fused Azocines from ortho-ortho′-Functionalized Biaryls F o r m a t i o n o f P h e n a n t h r i d i n e s a n d D i a r e n e -F u s e d A z o c i n e s This work is kindly dedicated to Prof. László Tőke on the occasion of his 75 th birthday.Abstract: Phenanthridines and azocines fused to two benzene rings or one benzene and one pyridazinone ring, which are otherwise difficult to access, were prepared via two new extensions of the tertamino effect. The synthetic pathway includes three steps: i) Suzuki reaction of an ortho-functionalized phenylboronic acid with orthodisubstituted benzenes or pyridazinones; ii) the Knoevenagel condensation reaction of the biaryl aldehydes formed with active methylene compounds to obtain vinyl derivatives or, through their cyclization, phenanthridines via a tert-amino effect; and iii) thermal isomerization of vinyl or phenanthridinium compounds to fused azocines via another type of tert-amino effect.

Facile Construction of 3,4‐dihydro‐2H‐1,2,4‐Benzothiadiazine 1,1‐Dioxides via Redox‐Neutral Cascade Condensation/[1,7]‐Hydride Transfer/Cyclization

“…Initially, eight‐membered aza‐heterocycle was construction by Mátyus et al. via the first fascinating [1,7]‐HT/cyclization, in which the hydride acceptor moiety needed to be installed beforehand, resulting in low step‐economy [22,24a] . Very recently, an amazing sequential [1,7]‐ & [1,5]‐hydride shift/cyclization process has been illustrated by Mori et al.…”

C(sp3)–H cyclizations of 2-(2-vinyl)phenoxy-tert-anilines

“…Or could it be a mixture of the two? The main characteristics of the sigmatropic rearrangement, like 39 / TS (39), are that the process is solvent independent (no ionic character that this hydride shi is between the two sides. The calculated TS enthalpies are not too high, between 100-130 kJ mol −1 , which is lowered by the quantum tunnelling effect by even 20 kJ mol −1 .…”

“…Cyclizations of fused bicyclic ( 3 → 4 ) and biaryl systems ( 5 → 6 , 7 → 8 ) with the interacting dialkylamino and vinyl groups in ortho , ortho ′ or ortho and peri positions furnished the respective 7–9 membered rings, besides the formation of novel zwitterionic phenantridium or benzo[ d , e ]quinolinium systems through a Michael type addition in several cases. 39,40 Starting from triaryl derivatives, 10-membered azecine rings could be attained ( 12 → 13 ). 41 As examples of nondirectly connected biaryl systems, where a sigmatropic hydrogen transfer could a priori be excluded, the cyclization of biphenyl derivatives bridged with a methylamino- N -methyl group ( 9 → 10 ) or an oxygen between the phenyl rings ( 14 → 15 ) were studied.…”

tert-Amino Effect-Promoted Rearrangement of Aryl Isothiocyanate: A Versatile Approach to Benzimidazothiazepines and Benzimidazothioethers

“…Molecular rearrangement facilitated by the tert -amino effect, a term coined by Meth-Cohn and Suschitzky in 1972, is an efficient synthetic tool for the construction of nitrogen-containing heterocyclic compounds . Particularly, the tert -amino effect-promoted 1, n -hydride transfer/cyclization processes, referred to as type 1–3 reactions of the t -amino effect according to Meth-Cohn’s classification, are the most concerned reactions owing to their high efficiency and remarkable step/atom economy, which have attracted considerable interest because of their reliable capability (Scheme b) .…”