Photoarylation, heteroatom-directed

Diphenyl ether undergoes cleavage on ultraviolet irradiation in alcoholic solvents,but irradiation of dilute solutions in cyclohexane in the presence of an equimolar amount of iodine as oxidant produces dibenzo-furan As in heteroatom-directed photoarylations, a conrotatory elec-trocyclization producing the carbonyl ylide intermediate 40 (Scheme 1) is... 

The process known as heteroatom-directed photoarylation" is also believed to involve a conrotatory photocyclization followed by a suprafacial... 

A novel process for the construction of benzodihydrofurans via a procedure involving a heteroatom-directed photoarylation provided the basis for another total synthesis of ( )-lycoramine (299) (Scheme 32) (167). Thus, 339, which was obtained from 1,3-cyclohexanedione in two straightforward steps, was converted to 340 by sequential treatment with LiAlH4, methyl chloroformate, and aqueous acid. Epoxidation of 340 with alkaline hydrogen peroxide followed by... 

Heteroatom directed photoarylation. Approaches to the synthesis of morphine and the study of a stereospecific benzodihydrofuran photorearrangement... 

Heteroatom directed photoarylation synthesis of a tetracyclic morphine structural analog... 

Several reviews have been published within the year which are of general relevance to the photoreactions of aromatic compounds. The subjects of these reviews include photochemistry in ionic liquids and in isotropic and anisotropic media, organic synthesis utilizing photoinduced electron-transfer reactions," heteroatom-directed photoarylation processes, photochromism, and photochemical molecular devices. Reviews more directly pertinent to the sections in the present chapter include those of the photoisomerization of five-membered heteroaromatic azoles, the photocycloaddition of benzene derivatives to alkenes, Diels-Alder additions of anthracenes, advances in the synthesis of polycyclic aromatic compounds, diarylethene-based photochromic switches, the photo-Fries rearrangement, and the application of Diels-Alder trapping of photogenerated o-xylenols to the synthesis of novel compounds. " A number of chapters in the two recently published handbooks of photochemistry and photobiology and in the revised edition of the text on photochromism are also pertinent to the current subject matter. 

The only photochemical preparation of indolines in 1980 has been reported by Schultz and Sha. They have extended some earlier work of their own on the preparation of dihydro-benzofurans, -thiophenes, and -selenoles by heteroatom-directed photoarylation. The latest work has emphasized that this photoarylation technique should be the method of choice for preparing indolines that were previously only accessible with great difficulty [e.g. (284) - (285)]. 

Dihydrofurans.—As part of a general study on heteroatom-directed photoaryl-ation, Schultz and his co-workers have studied the irradiation of aryloxyenones (Scheme 9). The products are tricyclic dihydrofurans a wide range of functionality in the phenol can be tolerated, and yields are high (32—100%). The method has been used in the synthesis of the Amaryllidaceae alkaloid lycoramine and a tetracyclic morphine structural analogue. ... 

As a part of a general study related to heteroatom-directed photoarylation, Schultz and his co-workers have studied the photolysis of various vinyl sulphides. The initial products are dihydrothiophens which may be further transformed into thiophens or other products (e.g. Scheme 28). As with the... 

---