An Alternative Synthesis of 2-Alkylidene-3,4-dihydro-2H-1,4-benzoxazines by Intramolecular Gold-Catalyzed Hydroalkoxylation of 2-(Prop-2-yn-1-ylamino)phenols
An efficient gold-catalyzed procedure to synthesize 2-alkylidene-3,4-dihydro-2H-1,4-benzoxazines has been developed starting from 2-alkynyl-substituted phenols. This is an intramolecular hydroalkoxylation reaction on alkynes tethered to a phenol moiety that represents a valuable alternative to the already reported transition-metal-catalyzed procedures.
Palladium-Catalyzed Heteroannulation Leading to Heterocyclic Structures with Two Heteroatoms: A Highly Regio- and Stereoselective Synthesis of (<i>Z</i>)-4-Alkyl-2-alkyl(aryl)idene-3,4-dihydro-2<i>H</i>-1,4-benzoxazines and (<i>Z</i>)-3-Alkyl(aryl)idene-4-tosyl-3,4-dihydro-2<i>H</i>-1,4-benzoxazines
作者:Nitya G. Kundu、Gopeswar Chaudhuri、Anup Upadhyay
DOI:10.1021/jo000826j
日期:2001.1.1
triethylamine at room temperature to yield 2-[N-alkyl(benzyl)-N-(3-aryl-prop-2'-ynyl)]-aminophenyl tosylates 8 in extremely good yields (72-96%). The latter could then be cyclized with KOH in ethanol-water to Z-9 in a highlyregio- and stereoselective manner. Similarly, palladium-copper-catalyzed reaction of 2-(prop-2'-ynyloxy)aniline (21) with aryl iodides 7 led to 22-26 which after tosylation and cyclization