Palladium-Catalyzed Highly Regio- and Stereoselective Synthesis of 4-Alkylidene-4H-3,1-benzoxazines from N-Acyl-o-alkynylanilines

Abstract

The highly regio- and stereoselective 6-exo-dig mode cyclization of N-acyl-o-alkynylanilines producing 4-alkylidene-3,1-benzoxazines occurred unpredictably by use of a proper catalyst [Pd(OAc)(2)] and an effective additive (acetic acid) under suitable reaction conditions.

Synergistic Effect of Palladium and Copper Catalysts: Catalytic Cyclizative Dimerization of ortho‐(1‐Alkynyl)benzamides Leading to Axially Chiral 1,3‐Butadienes

“…Indeed, Pd-catalyzed cyclization of alkynamides followed by trapping of the resulting vinylpalladium by an external double bond is known. [22] However, detailed studies will be required to determine the exact mechanism and the role of CuA C H T U N G T R E N N U N G (OAc) 2 in this reaction. Nonetheless, the spectacular modification of the reaction pathway catalyzed by the Pd II /Cu II couple versus that catalyzed by a single metal (Pd, or Cu) is truly remarkable.…”

Iron(III) Chloride/Diorganyl Diselenides Promoted Regio‐ and Stereoselective Cyclization of ortho‐Alkynylanilides: Synthesis of (Z)‐4‐(chalcogen)methylenebenzoxazines

“…[19] We started our research on the cyclization reaction by studying the most appropriate experimental conditions to deliver the desired products in high yields with a low rate of by-products. [19] We started our research on the cyclization reaction by studying the most appropriate experimental conditions to deliver the desired products in high yields with a low rate of by-products.…”

“…[15] The cyclization of ortho-alkynylanilides is an appropriate way to produce nitrogen heterocycles, such as indoles and benzoxazines. [19] This method involved a regio-and stereoselective 6-exo-dig cyclization of N-acyl-ortho-alkynylanilines producing 4-alkylidene-3,1-benzoxazines 3 (Scheme 1) by using PdA C H T U N G T R E N N U N G (OAc) 2 as catalyst and acetic acid as additive. [18] An improved procedure for the cyclization of ortho-alkynylanilides was successfully applied by the Saito group.…”

Isocyanide Cyclization Reactions: 4‐Methylene‐4H‐benzo[d][1,3]oxazine, 3‐Benzyl‐4‐methylene‐3,4‐dihydroquinazolines and 3‐(4‐Benzyl)‐3H‐quinazolin‐4‐ones – Experiment and Theory

“…[4] Substituted derivatives of compounds 4 have been prepared by Saito et al by Palladium-catalysed cyclization of N-acyl-o-alkynylanilines. [14] Reactions of 3 with Amines: Synthesis of Dihydroquinazolines 6 and Quinazoline-4-ones 9…”