Modular synthesis of (E)-cinnamaldehydes directly from allylarenes via a metal-free DDQ-mediated oxidative process

Abstract

An efficient synthesis of (E)-cinnamaldehydes by a metal-free DDQ-mediated oxidative transformation of allylarenes was developed. The protocol provides a practical method to prepare diverse (E)-cinnamaldehydes with broad functional group tolerance in good to excellent yields, including easy access to natural products randainal and geranyloxy sinapyl aldehyde from plant extracts. Finally, the mechanism of a single-electron transfer process was proposed.

Structure and Properties of Oxidized Chitosan Grafted Cashmere Fiber by Amide Covalent Modification

“…In general, because HNO3 includes small amounts of nitrogen oxides (e.g., NO, NO2, N2O3, and N2O5, etc. ), the oxidation of polysaccharide mixtures by HNO3 is accompanied by a catalyst (e.g., H3PO4) and an initiator (e.g., NO2 or HNO2) at a lower temperature [27]. An explanation of the oxidation mechanism was reported in our previous article [25] and is briefly described as follows.…”

“…Oxidants can easily penetrate into the interior of chitosan and increase the accessibility of oxidation reaction among chitosan and is beneficial to increase the DO of chitosan [28]. Carboxyl groups are formed in the oxidized chitosan molecules, which accordingly generates internal salt bonds and intramolecular hydrogen bonds with the amino, hydroxyl, and other polar groups in the molecules among chitosan macromolecules [27]. As a result, the oxidized chitosan molecules are curled in solution without parallel arrangement of microfiber structures, eventually precipitating into spherical crystals.…”

Methylene Capping Facilitates Cross-Metathesis Reactions of Enals: A Short Synthesis of 7-Methoxywutaifuranal from the Xylochemical Isoeugenol

“…A synthesis from vanillin ( 3 ) via aldol condensation requires additional protecting group steps and proceeds in a very low yield . The synthesis of coniferyl aldehyde ( 5 ) by allylic oxidation has been reported with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as an oxidant but only for O -protected eugenol derivatives. , The protecting group-free oxidation of eugenol ( 1 ) to coniferyl aldehyde ( 5 ) makes use of fermentative methods, and reports thereon are restricted to the patent literature. , …”

“…18 The synthesis of coniferyl aldehyde (5) by allylic oxidation has been reported with 2,3dichloro-5,6-dicyanobenzoquinone (DDQ) as an oxidant but only for O-protected eugenol derivatives. 19,20 The protecting group-free oxidation of eugenol (1) to coniferyl aldehyde (5) makes use of fermentative methods, and reports thereon are restricted to the patent literature. 21,22 An approach to coniferyl aldehyde (5) that has surprisingly not been mentioned in the literature so far is the cross metathesis 23 of isoeugenol (2) with α,β-unsaturated aldehydes 7.…”

Iron(III)/O2-Mediated Regioselective Oxidative Cleavage of 1-Arylbutadienes to Cinnamaldehydes

“…Due to low toxicity, these are also used as fungicides and pesticides . While cinnamaldehydes are prepared by different methods, a recent paper used allyl benzenes in oxidation with DDQ to prepare cinnamaldehydes, although similar procedures with allyl/alkyl benzene were reported earlier . An alternative method selectively cleaving the terminal double bond of 1-arylbutadienes to cinnamaldehydes (and not benzaldehydes), without overoxidation to cinnamic acid or benzoic acid, with a wider substrate scope would be highly desirable.…”