Synthesis of 2H-1-Benzopyrans by Pd-Catalyzed Cyclization of <i>o</i>-Allylic Phenols
作者:Richard C. Larock、Lulin Wei、Timothy R. Hightower
DOI:10.1055/s-1998-1709
日期:1998.5
Derivatives of 2H-1-benzopyran (1), also known as chromenes, are prominent natural products of many genera of the Asteraceae possessing a wide range of valuable physiological activities. They are also useful intermediates in the synthesis of complex natural products, such as pterocarpans.
2<i>H</i>-Chromenes Generated by an Iron(III) Complex-Catalyzed Allylic Cyclization
作者:L. Calmus、A. Corbu、J. Cossy
DOI:10.1002/adsc.201500058
日期:2015.5.4
A straightforward method based on an iron(III) complex‐catalyzed cyclization of 2‐(1‐hydroxyallyl)phenols is reported to access a large variety of 2H‐chromenes. This method was applied to the total synthesis of a natural product, tephrowatsin B.
Synthesis of 2<i>H</i>-Chromenes via Hydrazine-Catalyzed Ring-Closing Carbonyl-Olefin Metathesis
作者:Yunfei Zhang、Janis Jermaks、Samantha N. MacMillan、Tristan H. Lambert
DOI:10.1021/acscatal.9b03656
日期:2019.10.4
The catalytic ring-closing carbonyl-olefin metathesis (RCCOM) of O-allyl salicylaldehydes to form 2H-chromenes is described. The method utilizes a [2.2.1]-bicyclic hydrazine catalyst and operates via a [3 + 2]/retro-[3 + 2] metathesis manifold. The nature of the allyl substitution pattern was found to be crucial, with sterically demanding groups such as adamantylidene or diethylidene offering optimal
Asymmetricaddition of arylboronicacids to 2H-chromenes proceeded in the presence of a hydroxorhodium/chiral diene catalyst to give 3-arylchromanes in high yields with high enantioselectivity. The reaction involves 1,4-Rh shift before protonation to release the addition product and to regenerate the hydroxorhodium species.
Synthesis of 2<i>H</i>-Chromenes through the Reduction of Chromones with 9-BBN
作者:Tetsuya Eguchi、Yukio Hoshino
DOI:10.1246/bcsj.74.967
日期:2001.5
reduced to 2H-1-benzopyrans through the 1,2-addition of 9-borabicyclo[3.3.1]nonane. Although transition-metal complexes did not have a catalytic effect on the reaction, only by using palladium(II) chloride, could both 2H-1-benzopyran and dihydro-1-benzopyran be obtained to a similar extent. Also, the reduction of chromone using other organoboranes led not to 2H-1-benzopyran, but rather to chromanone through