The Aryne Ene Reaction

Abstract

Intermolecular aryne ene reactions present opportunities to arylate a wide range of unsaturated substrates in a single step, whilst intramolecular reactions provide expedient access to valuable benzofused carbo- and heterocyclic frameworks. This short review will chart the development of the aryne ene reaction from initial reports that rationalise unexpected by-product formation in competing [4+2] and [2+2] cycloadditions through to its exploitation in contemporary synthetic methodology.

Stereoselective Alder-Ene Reactions of Bicyclo[1.1.0]butanes: Facile Synthesis of Cyclopropyl- and Aryl-Substituted Cyclobutenes

“…We questioned whether other strained π-bonds might also engage with BCBs, thus affording unique small-ring product architectures from these readily accessible building blocks. Here, we describe the strain-relief-driven Alder-ene reaction of polyfunctionalized BCBs with cyclopropenes, generated in situ from visible light-promoted decomposition of vinyl diazo compounds ( 2 , Figure b), to give cyclopropyl-substituted cyclobutenes ( 3 ); and also, the development of highly efficient ene reactions of BCBs with a selection of arynes generated under mild reaction conditions from arylsilane triflates 4 to give arylated cyclobutenes 5 . These reactions display a broad scope and high stereoselectivity; mechanistic studies support the involvement of an asynchronous concerted reaction pathway and highlight the importance of electronic effects in these transformations.…”

3-Halo-5,6-dihydro-4H-1,2-oxazine N-oxides as synthetic equivalents of unsaturated nitrile oxides in the [3 + 2]-cycloaddition with arynes: synthesis of substituted 3-vinyl-1,2-benzisoxazoles

“…Indeed, the presence of a styrene fragment allows subsequent [4 + 2]-annulation. 26 However, in contrast to the closest literature examples, 26 b the C(8a)C(9) double bond in intermediate 11 did not undergo ene-reaction with the second molecule of aryne, but hydrogen 1,3-migration occurred producing dihydrophenanthrene-substituted product 12 in good yield. It may be explained by the relative acidity of the C(4b)–H proton due to possible conjugation with the CN bond.…”

Pseudocyclic Arylbenziodoxaboroles as Water-Triggered Aryne Precursors in Reactions with Organic Sulfides

“…Benzyne and other aryne intermediates have found broad application in modern organic synthesis . Common benzyne precursors require activation via application of heat, irradiation, a strong base (NaNH 2 , BuLi, RMgBr, LiHMDS, etc.…”

“…Benzyne and other aryne intermediates have found broad application in modern organic synthesis. 1 Common benzyne precursors require activation via application of heat, irradiation, a strong base (NaNH 2 , BuLi, RMgBr, LiHMDS, etc. ), or the anhydrous fluoride anion, which is also a strong base and requires special handling to avoid moisture.…”