Rapid Photoassisted Access to N,O,S‐Polyheterocycles with Benzoazocine and Hydroquinoline Cores: Intramolecular Cycloadditions of Photogenerated Azaxylylenes

Abstract

Ring the changes: A new photoassisted approach to give conformationally constrained N,O,S‐polyheterocyclic scaffolds of unprecedented topologies was achieved by intramolecular [4+4] and [4+2] cycloadditions of photogenerated o‐azaxylylenes (23 examples; see scheme). The precursors can be readily assembled by simple and high‐yielding reactions, thus making this a powerful synthetic method amenable to high‐throughput diversity‐oriented synthesis.

Approach for Expanding Triterpenoid Complexity via Divergent Norrish-Yang Photocyclization

“…However, the use of light as a reagent in diversity oriented synthesis is limited. 21–22 In relation to natural products, a single report by the group of de la Torre 23 describes an elegant application of a [2+2] cycloaddition and Paterno-Buchi reaction to the synthesis of diverse polycyclic terpene-like structures from readily available sesquiterpene Sclareolide.…”

Conformationally Constrained Penta(hetero)cyclic Molecular Architectures by Photoassisted Diversity‐Oriented Synthesis

“…In this context, further elaboration of the molecular architectures was achieved by reacting the [4+4] and [4+2] photoproducts with bromonitrile oxide generated in situ from dibromoformaldoxime 21 . This reaction was initially explored and optimized on model compounds 14 and 15 , synthesized according to the previously published procedures 12 , Scheme 5. In both cases the 1,3-dipolar cycloaddition of bromonitrile oxide occurs from the exo -face.…”

“…The main focus of the research efforts in our laboratory in recent years has been the utilization of azaxylylenes generated via excited state intramolecular proton transfer (ESIPT) in aromatic o -aminoketones in intramolecular [4+4] or [4+2] cycloaddition reactions to tethered unsaturated moieties – alkenes, furans, thiophenes, and pyrroles 12, 13 – to yield novel N,O,S-polyheterocycles 14 , Scheme 1.…”

Asymmetric Brønsted Acid Catalyzed Substitution of Diaryl Methanols with Thiols and Alcohols for the Synthesis of Chiral Thioethers and Ethers

“…[6] Nevertheless,a za-ortho-quinone methides,especially compared to their oxygen-containing analogous ortho-quinone methides, [7] have not been adequately investigated to date.P articularly in the area of asymmetric synthesis,only afew examples exist. [11,12] Thev ariety of possibilities may be surprising;h owever, in reality it is limited by the predominantly harsh reaction conditions.M any substrates are not compatible with the use of overstoichiometric amounts of base,t he exposure to high temperatures (often under flash-vacuum-pyrolysis conditions), or continuous irradiation. [11,12] Thev ariety of possibilities may be surprising;h owever, in reality it is limited by the predominantly harsh reaction conditions.M any substrates are not compatible with the use of overstoichiometric amounts of base,t he exposure to high temperatures (often under flash-vacuum-pyrolysis conditions), or continuous irradiation.…”