Terminal 2-arynes

A three-compruient addition for the hydration of alkynes was accomplished to form efficiently 3-oxabicyclo[3.1.0]hexanes from 2-(arylmethylene)cyclopropyl-carbinols, terminal arynes, and alcohols (Scheme 12) [126]. 

THF at room temperature to produce substituted phenylallenes (231). Various arynes and terminal and internal alkynes can be used. The reaction of alkyne without propar-gylic hydrogen gave an acetylenic C-H addition product (a phenylalkyne) and a dehydro-Diels-Alder product (a phenanthrene).266... 

Another family that can participate in metal-catalyzed cocyclotrimerization with arynes are the terminal allenes (e.g. 162). This cocycloaddition is best catalyzed by Ni(0), and leads in the case of 162 to 9-cyclohexyl-10-methylene-9,10-dihydrophenanthrene (163). For monosubstituted allenes the reaction appears to be highly selective, since only the internal C-C double bond of the allene participates in the cocyclotrimerization. With disubstituted allenes, mixtures of the two possible regioisomers are obtained as the result of the participation of both C-C double bonds in the cycloaddition reaction [79,80] (Scheme 46). 

SCHEME 51 MCR involving arynes, N-heterocycles, and terminal alkynes [73],... 

F. Sha, X. Huang, A multicomponent reaction of arynes, isocyanides, and terminal alkynes highly chemo- and regioselective synthesis of polysubstituted pyridines and isoquinolines, Angew. Chem. Int. Ed. 48 (2009) 3458-3461. 

M. Jeganmohan, S. Bhuvaneswari, C.-H. Cheng, Synthesis of N-arylated 1,2-dihydroheteroaromatics through the three-component reaction of arynes with N-heteroaromatics and terminal alkynes or ketones, Chem. Asian J. 5 (2010) 153-159. 

Zhang s and Yoshida s groups, independently, demonstrated that the dimerizative insertion of arynes into a C(sp)—H a-bond of terminal alkynes 53 was catalyzed efficaciously by a Au(I)-Cu(I) cocatalytic system [26a] or a Cu(I) catalyst [26b], respectively, giving 2-alkynylbiaryls 54 (Scheme 28.20). Each reaction begins with a nucleophilic attack by an in situ-generated alkynyl copper species toward an aryne. Also, a C(sp)-Br a-bond of alkynyl bromides 55 accepted the insertion of arynes under copper catalysis, and the reaction was also applicable to propargyl bromide 56 and allyl bromide 57 (Scheme 28.21) [27], An aryl copper species derived from the insertion of an aryne into a Cu—Br bond is a key intermediate in the reaction. 

Bhuvaneswari et al. [75] reported a copper-catalyzed three-component couphng of arynes, terminal alkynes, and activated alkenes, providing l-alkyl-2-alkynylben-zenes 108 (Scheme 5.72). 2-(Trimethylsilyl)-3,4-dimethylphenyl triflates 107 were used as benzene precursors. Reaction of terminal alkynes with Cu(l) species in the presence of CsF (or K COj) gives copper acetylides A. Alkynylcupration of the in situ-generated arynes B with cuprous acetylides A affords arylcuprous intermediates... 

SCHEME 5.72 Cu(I)-catalyzed three-component coupling of arynes, terminal alkynes, and activated alkenes. 

The common reaction mode for arynes and olefins is the ene process that results in a phenylation accompanied by a double bond shift. Such transformations can also be achieved with aza analogs (Schiff bases) of terminal or internal olefms. ... 

This nomenclature type uses substractive prefixes to indicate removal of atoms or groups of atoms from a trivially or systematically named parent structure. While additive nomenclature is used above all for hydrogenated cyclic systems, subtractive nomenclature focuses primarily on the opposite phenomenon, i. e. introduction of unsaturation. This has already been dealt with extensively in the discussions relating to hydrocarbon systems, where the terminal syllables. .. ene and. ..yne signify loss of two and four hydrogen atoms with concomitant formation of a double and triple bond, respectively. A more explicit symbolization of dehydrogenation in the guise of a subtractive prefix is particularly recommendable for certain natural products of the steroid and carbohydrate series as well as for dehy-droarenes (less precisely also named arynes) and dehydroannulenes. 

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