Corrigendum: A General Synthesis of Alkenyl‐Substituted Benzofurans, Indoles, and Isoquinolones by Cascade Palladium‐Catalyzed Heterocyclization/Oxidative Heck Coupling

Palladium‐Catalyzed 6‐endo‐Selective Oxycyclization–Alkene Addition Cascades of ortho‐Alkynylarylcarboxamides and α,β‐Unsaturated Carbonyl Compounds

“…Under the appropriate PdI 2 ‐ or PdCl 2 /KI‐catalyzed conditions, the conjugate addition pathway operates to the exclusion of the alternative alkenylation reaction, whereas PdBr 2 or PdCl 2 (without added KI) are much less effective. Although the effect of the iodide anion on these reactions cannot be conveniently rationalized at this point, these overall observations add to a number of recent reports that highlight the beneficial effect of iodide anions in cycloisomerizations10 and other palladium‐catalyzed reactions 4,6b,6c,11…”

“…We previously reported that under typical conditions for the formation of alkenes 5 , which included PdCl 2 (PPh 3 ) 2 as the catalyst with KI (0.5 equiv.) as the additive in N , N ‐dimethylformamide (DMF) under air at 80 °C, the reaction of 3a with methyl vinyl ketone provided 6a in 20 % yield in addition to the expected major product 5a (Table 1, Entry 1) 6b,6c. We have subsequently found that the formation of 6a is favored by lowering the reaction temperature and using a phosphine‐free palladium catalyst (Table 1, Entries 2 and 3).…”

A Practical Protocol for Three-Component, One-Pot, Stepwise Sonogashira-Heterocyclization-Heck Couplings

“…[22][23][24][25][26][27][28][29] While this is due in part to some interesting biological activities displayed by five-and six-membered cyclic imidates 25,29 and to their use as ligands in asymmetric catalysis, 30 it is also noted that the preparation of these compounds has revealed a rather unexpected strong tendency of 2-alkynylbenzamides to undergo O-cyclization in palladium-catalyzed processes. 8,26,27,31,32 Furthermore, the regiochemistry of the cyclization has been found to be variable, depending on the reaction conditions. For example, under the oxidative Heck conditions of Scheme 1, in-termediate 2-alkynylbenzamides 3 undergo highly selective 6-endo-cyclizations, 8,31 whereas an alternative coupling with aryl halides has been reported with 5-exo regioselectivity, 26 and reactions cocatalyzed by palladium and copper led to oxidative dimerization products, also with 5-exo regiochemistry.…”

“…8,26,27,31,32 Furthermore, the regiochemistry of the cyclization has been found to be variable, depending on the reaction conditions. For example, under the oxidative Heck conditions of Scheme 1, in-termediate 2-alkynylbenzamides 3 undergo highly selective 6-endo-cyclizations, 8,31 whereas an alternative coupling with aryl halides has been reported with 5-exo regioselectivity, 26 and reactions cocatalyzed by palladium and copper led to oxidative dimerization products, also with 5-exo regiochemistry. 27 Significantly, in the one-pot preparation of 4, the formation of side-products, presumably regioisomers and/or dimers, was suppressed with the addition of catechol, which was suspected to act as a copper scavenger.…”

“…The cyclization-intermolecular Heck coupling cascade of 2alkynylbenzamides and alkenes has been shown to also provide cyclic amidates in a 6-endo-selective manner. 31 By performing the coupling in the presence of the copper salts carried over from the Sonogashira coupling, the effect of copper on the regiochemistry and coupling efficiency would be evaluated in the absence of any intramolecular bias. We now report that the three-component process from haloarenecarboxamides 1 (and related substrates), terminal alkynes and ethyl acrylate is also effective without isolation of the intermediate Sonogashira adducts, and that cyclic imidate type coupling products are obtained with very high 6-endo selectivity.…”