Metal-free synthesis of phosphinoylchroman-4-ones via phosphinoylation/cyclization cascade mediated by K₂S₂O₈

Abstract

A variety of chroman-4-ones bearing phosphine oxide motifs were conveniently synthesized from readily available diphenylphosphine oxide and alkenyl aldehydes via a metal-free tandem phosphinoylation/cyclization protocol. The reaction utilizes K2S2O8 as oxidant and proceeds in DMSO-H2O at environmentally benign conditions with broad substrate scope and afforded the title compounds in moderate yields.

Redox-neutral and metal-free synthesis of 3-(arylmethyl)chroman-4-ones via visible-light-driven alkene acylarylation

“…Chroman-4-one scaffolds, a class of important oxygen-containing structural motifs, are ubiquitous in a plethora of natural products, drug candidates, and biologically active molecules ( Albrecht et al, 2005 ; Nibbs and Scheidt, 2011 ; Friden-Saxin et al, 2012 ; Lee et al, 2014 ; Seifert et al, 2014 ; Emami and Ghanbarimasir, 2015 ; Kumar et al, 2017 ; Mayuri et al, 2017 ). In the past years, the radical-initiated cascade cyclization strategy has attracted great attention for the construction of chroman-4-one scaffold and other (hetero)cyclic frameworks ( Zhao et al, 2016 ; Yang et al, 2017 ; Hu et al, 2018a ; Hu et al, 2018b ; Liu et al, 2019 ; Sheng et al, 2019 ; Xiao et al, 2019 ; Zhou et al, 2019a ; Das et al, 2020 ; Han et al, 2020 ; Huang et al, 2020 ; Liu et al, 2020 ; Mei et al, 2020 ; Xiong et al, 2020 ; Diana et al, 2021 ). Particularly, the photocatalytic radical-initiated cascade cyclization, including two mechanistically distinctive pathways, has emerged as an elegant, green, and powerful strategy for the synthesis of such scaffold and its derivatives.…”