Lewis acid promoted dual bond formation: facile synthesis of dihydrocoumarins and spiro-tetracyclic dihydrocoumarins

Abstract

Lewis acid (FeCl3) mediated dual bond (C-C and C-O) formation for synthesis of 3,4-dihydrocoumarins is presented. This method has successfully delivered a number of dihydrocoumarins containing dense functionalities on the aromatic ring. Significantly, the present method enabled achieving dihydrocoumarins with tertiary as well as quaternary carbon atoms at the benzylic position. Gratifyingly, the novel spiro-tetracyclic lactones have also been dextrously prepared using this process.

Chemoselective Dual Functionalization of Phenols via Relay Catalysis of Borane with Different Forms

“…In this borane-catalytic system, the initial ortho-alkylation process not only delivers an unusual dearomatized complex III, but also produces the requisite Brønsted acid catalyst (B 3 ) in the subsequent lactonization. This transformation affords a series of benzofuranones [43][44][45][46][47][48][49] and dihydrocoumarins, 50,51 which are important motifs in natural products, biologically significant compounds, and materials for chemical biology, in moderate to high yields and high chemoselectivities.…”

An Efficient Synthesis of Coumarin Derivatives Using a SBA-15 Supported Cobalt(II) Nanocatalyst

“…Pechmann condensations generally involve the reaction of phenolic compounds with a carboxylic acid or an ester containing a b-carbonyl group to generate an intermediate that undergoes dehydration to the final coumarin product. Several protocols have extensively covered the synthesis of coumarin derivatives via Pechmann condensation, mostly catalysed by homogeneous acidic catalysts including H 2 SO 4 , P 2 O 5 [10], trifluoroacetic acid [11] as well as different metal salts such as FeCl 3 , TiCl 4 , InCl 3 , ZrCl 4 [12][13][14][15], Bi(NO 3 ) 3 Á5(H 2 O) [16] and Cu(CH 3 CN) 4 PF 6 [17]. The use of homogeneous acid catalysts possesses inherent corrosion, separation, product isolation and purification and catalyst recycling issues, highly detrimental from the practical point of view.…”

Palladium-Catalysed Coupling and Acid-Mediated Cyclisation: Synthesis of Fluorenones and Fluorenes

“…To begin with, it was anticipated that fluorenone 4aa could be obtained in a sequential one-pot operation by employing an intramolecular Friedel-Crafts acylation of the Suzuki product biphenyl ester 3aa generated in situ (Table 1). Based on our earlier achievements in the synthesis of indanones 17 and dihydrocoumarins, 18 it was conceived that Friedel-Crafts acylation in situ of relatively inert biphenyl ester 3aa could only be feasible in the presence of a SYNOPEN2 5 0 9 -9 3 9 6 Georg Thieme Verlag Stuttgart • New York 2018, 2, 268-275 paper en D. R. Kumar et al…”