Synthesis of Benzofuans, Tetrahydrobenzopyrans, and Related Cyclic Ethers via Cyclic Carbopalladation

Oxa-Enediynes: Probing the Electronic and Stereoelectronic Contributions to the Bergman Cycloaromatization

“…Deprotection of 27 to liberate 20 was again easily achieved using TBAF. The half-life of 20 was found to be approximately 15 h at physiological temperature, in good empirical agreement with its calculated intraacetylenic (c-d) distance of 3.346 Å. Incubation of 20 in the presence of 1,4-cyclohexadiene (30 equiv) led to conversion (>80%) to tricyclic product 23, 15 presumably via the intermediacy of diradical 22. As such, the process represents an efficient route to substituted isochromans.…”

Cyclic Carbopalladation. A Versatile Synthetic Methodology for the Construction of Cyclic Organic Compounds

“…The development of the procedures for the synthesis of carbocycles via cyclic Heck reaction was further delayed by several years and was very sluggish until the late 1980s. Several examples reported by Heck, 11 Grigg, 12 and ourselves 13 to be the only ones reported as of a decade ago. However, intensive studies made since the late 1980s have firmly established that the cyclic Heck reaction represents a novel and versatile methodology for the construction of both carbocycles and heterocycles.…”

“…However, intensive studies made since the late 1980s have firmly established that the cyclic Heck reaction represents a novel and versatile methodology for the construction of both carbocycles and heterocycles. Besides those by the authors, studies by Larock, Grigg, and Overman led to subsequent extensive applications of the cyclic Heck reaction. Some more recent developmental works by Fuchs 18a,b and others are also noteworthy.…”

Intramolecular Photoarylation of Alkenes by Phenyl Cations

“…22 The nature of the intermediate is expected to have a major effect on the regioselectivity of the cyclization. As an example, phenyl radicals generated from the corresponding o ‐allyloxyphenyl iodides or bromides by means of triorganogermanium hydrides,23a tin dithiocarbonates,23b alkylsamarium( III ) reagents,23c reduction of aryl diazonium salts,23d cobalt complexes,23e and Pd complexes23f showed a marked preference for the 5‐ exo ‐trig cyclization,24 just as γ‐oxahexenyl radicals do 25. The same selectivity was observed when the radicals were obtained by photochemical means through an S RN 1 reaction,26a through photoinduced electron transfer with suitable donors,26b–d by direct irradiation of an aryl iodide,27 from phenyl diazonium salts in cyclodextrins (CDs),26e or through other photostimulated reactions 26f,g.…”