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A new method was developed for the photoinduced dearomatization of arenes through an intramolecular cycloaddition with aza-o-xylylenes generated by excited-state intramolecular proton transfer (ESIPT) in the readily available photoprecursors. The [2+4] topology of this cycloaddition is unprecedented for photo-dearomatizations of benzenoid aromatic carbocycles. It provides rapid access to novel heterocycles, cyclohexadieno-oxazolidino-quinolinols, as valuable synthons for a broad range of post-photochemical transformations., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Upon irradiation, cyclic imines containing o-amido groups are shown to produce reactive intermediates, amino azaxylylenes, which undergo intramolecular cycloadditions to tethered unsaturated pendants to yield complex N,O-heterocycles having an additional spiro-connected nitrogen heterocyclic moiety. Modular assembly of the photoprecursors allows expeditious increase of the complexity of the target poly-heterocyclic scaffolds with a minimal number of experimentally simple reaction steps. The photocyclization and subsequent postphotochemical transformations are accompanied by an increase of Lovering's fsp3 factor, thus producing unprecedented three-dimensional molecular architectures, and offering extended sampling of chemical space., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Upon irradiation, cyclic imines containing o-amido groups are shown to produce reactive intermediates, amino azaxylylenes, which undergo intramolecular cycloadditions to tethered unsaturated pendants to yield complex N,O-heterocycles having an additional spiro-connected nitrogen heterocyclic moiety. Modular assembly of the photoprecursors allows expeditious increase of the complexity of the target poly-heterocyclic scaffolds with a minimal number of experimentally simple reaction steps. The photocyclization and subsequent postphotochemical transformations are accompanied by an increase of Lovering's fsp3 factor, thus producing unprecedented three-dimensional molecular architectures, and offering extended sampling of chemical space. [ABSTRACT FROM AUTHOR]

Photogeneratedazaxylylenes undergo intramolecular cycloadditionsto 1,3,4-oxadiazole pendants, which are accompanied by concomitantrelease of dinitrogen, yielding functionalized ketopiperazinoquinolinolscontaining an oxirane moiety fused to the quinolinole moiety whilespiro-connected to diketopiperazine. These primary photoproducts arereactive versatile intermediates which can be further derivatizedunder nucleophilic SN1- or SN2-like ring openingof the oxirane moiety. The oxidized quinolinones undergo new rearrangementsunder the conditions of the Schmidt reaction, leading to unprecedentedtriazacanoindolinones. [ABSTRACT FROM AUTHOR]

The intramolecular photocyclization of amino azaxylylenes derived from o-amido imines, e.g. compounds (I), (IV), and (VII), leads to mixtures of [4 + 4] and [4 + 2] adducts. [ABSTRACT FROM AUTHOR]