Brønsted acid-catalysed intramolecular ring opening of 2-(aryloxymethyl)-3-aryloxiranes leading to trans-4-arylchroman-3-ols: scope and limitations

Abstract

A simple and metal-free method for the synthesis of a series oftrans-4-arylchroman-3-olsviaBrønsted acid-catalysed stereoselective intramolecular Friedel–Crafts alkylation of electron-rich arenes by tethered epoxides is developed.

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

“…The easy accessibility of racemic and enantiomerically pure epoxy substrates through a number of well-established epoxidation methods coupled with procedural simplicity, high atom economy, regio- and stereoselectivity of IFCEA cyclization make this methodology highly practical for the use in organic synthesis. Recently, we have reported the synthesis of diverse trans -4-arylchroman-3-ols via Brønsted acid catalysed regio- and stereoselective IFCEA cyclization of 2-(aryloxymethyl)-3-aryloxiranes [22–23]. The use of IFCEA cyclization as the key step is part of our long term objective of synthesizing chroman-based NPs and NPLMs and their subsequent application in medicinal chemistry.…”

Synthesis of diverse catechin congeners via diastereoselective intramolecular epoxy-arene cyclization

“…13 C NMR (100MHz, CDCl 3 ): δ 153. 9,148.0,142.5,129.0,128.6,126.9,122.5,117.2,115.2,114.6,69.7,66.5,55.5,50.2. Anal.…”

“…In this full paper, we summarize our fully efforts on the synthesis of a diverse selection of this class of molecules with special emphasis on the reaction conditions and substrate scope. 9 In addition, we report an efficient synthesis of cis-4-arylchroman-3-ols from the corresponding trans-4-arylchroman-3-ols. We also report, for the first time, the development of a novel synthetic route to chromanfused 2,3-dihydrobenzofurans from cis-4-arylchroman-3-ols.…”

“…M.P. : 114-115 o C. 1 H NMR (400 MHz,2H),1H),2H),6.89 (d,J = 9.1 Hz,1H),6.79 (dd,J = 3.0,9.1 Hz, 1H), 6.42 (d,J = 2.9 Hz,1H),4.15 (d,J = 10.5 Hz,1H),2H),1H), 3.67 (s, 3H). 13 C NMR (100MHz, CDCl 3 ): δ 153.…”

“…Column chromatography: 5-15% ethyl acetate in hexane as elution gradient. Yield of the product: 83% (95 mg 9,147.9,143.8,142.8,128.9,128.5,126.8,113.1,111.9,100.2,69.9,66.2,56.2,55.7,49.3. Anal.…”