One‐Pot Heck and Reduction: Application towards Efficient Synthesis of Flavans Promoted by Lewis Acid

Abstract

An effective two-step process for the synthesis of functionalized flavans is presented. The proposed route comprises onepot method involving Heck reaction with allylic alcohols and 2-iodophenols followed by reduction. These diols upon treatment with the Lewis acid mediated intramolecular cyclization, under mild reaction conditions, afforded the flavans.[a] N.

Single‐Column‐Based Heck Coupling, Condensation and Alkylation Strategy: Synthesis of 2‐Benzoyl‐2‐alkyl‐2,3‐dihydro‐1H‐inden‐1‐ones

“…We began our probe with ethyl 2‐iodobenzoate 1 a and allylic alcohol 2 a using the established Heck conditions [25,26] . So, initially the coupled keto‐ester 3 a was isolated for the sake of confirmation.…”

“…We began our probe with ethyl 2-iodobenzoate 1 a and allylic alcohol 2 a using the established Heck conditions. [25,26,33] So, initially the coupled keto-ester 3 a was isolated for the sake of confirmation. Thereafter, we have screened the best condition for synthesizing the 1,3 diketone 4 a in a one-pot fashion via the intermolecular Heck and intramolecular Dickmann type of condensation (For optimization study see the supporting information, Table S2).…”

“…The Heck reaction is known for its efficient C−C bond formation through the coupling between organic halides and olefins, using pallidum acetate as a conventional source for palladium, which presents a convenient method for carbon‐carbon bond formation at the unsubstituted vinylic position [23–26] . When allylic alcohols are used as a source of olefins with aryl halides, the Heck reaction is known to form carbonyl compounds [27] .…”

“…[22] The Heck reaction is known for its efficient CÀ C bond formation through the coupling between organic halides and olefins, using pallidum acetate as a conventional source for palladium, which presents a convenient method for carboncarbon bond formation at the unsubstituted vinylic position. [23][24][25][26] When allylic alcohols are used as a source of olefins with aryl halides, the Heck reaction is known to form carbonyl compounds. [27] Although there has been a reasonable quantum of research on the synthesis of 1,3-diketones via the aforementioned strategies, there hasn't been much development on the same through the process of palladium-catalyzed coupling reactions, especially the indanone derivative of 1,3diketone.…”

Asymmetric hydrogenation and transfer hydrogenation in the enantioselective synthesis of flavonoids

“…The cyclization of 1,3-diarylpropan-1-ols is a well-established method for the synthesis of flavans. 98–100 In this context, the enantioselective reduction of dihydrochalcones provides access to the corresponding enantioenriched alcohols, leading to the asymmetric synthesis of flavans. This approach was employed by Merck's group in 2017 for the synthesis of flavan ( R )- 200 (Scheme 47).…”