Synthesis of Tetrahydrodibenzofuran and Tetrahydrophenanthridinone Skeletons by Intramolecular Nucleopalladation/Oxidative Heck Cascades

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

“…In the manuscript in ref. 6a, the structures were also incorrectly displayed, therefore this paper is corrected by another Addendum/Correction 6b. In any event, in common with the processes leading to iminoisobenzofurans mentioned above,3,4 the Pd‐catalyzed formation of 11 from 2‐alkynylbenzamides 7 also follows an initial O ‐cyclization pathway, albeit of the 6‐ endo‐dig type, therefore giving rise to a regiochemically different family of products.…”

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

“…For example, the sequential introduction of reagents in a certain order may be a requirement for success. [3][4][5][6][7][8][9] Whatever the actual protocol, the advantages of these types of operational strategies usually include lower costs, a more expeditious procedure, fewer purifications, and often, higher overall yields. When the consecutive steps in a multicomponent process include metal-catalyzed reactions, 6,[10][11][12][13][14][15][16][17][18][19] one particular challenge is the finding of a so-called 'multitask catalyst' 4,6 that is suitable for all the different steps involved in the overall transformation.…”

“…For example, onepot, consecutive Sonogashira-cycloisomerization reactions have been employed extensively. 20 However, reports on the related process involving an additional coupling after the cyclization step (Sonogashira-cyclization-coupling) are scarce, 3,5,[7][8][9][10][11] particularly when the new coupling takes place under oxidative conditions. 7,8,10a,21 A key problem in this case is the difficulty in running the airsensitive Sonogashira reaction and an oxidative coupling process (e.g., Heck) under a unique set of conditions, a situation where a one-pot, stepwise procedure may be advantageous.…”

“…The reaction is performed in a one-pot, stepwise fashion without isolation of the intermediate Sonogashira adduct 3 (Scheme 1). 8 The same strategy has been employed in the preparation of 3-(1-alkenyl)benzofurans in a microwaveassisted process. 10a In fact, the cyclic imidate substructure embedded in products 4 has been the subject of significant attention in the literature.…”

“…[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.…”