Use of 4-Cyanocoumarins as Dienophiles in a Facile Synthesis of Highly Substituted Dibenzopyranones

Abstract

A new synthesis of dibenzopyranones 14 is reported via the Diels-Alder cycloaddition of 4-cyanocoumarins 12 with 1-silyloxydienes 10 to give the adducts 13 which are then converted into 14 in one step via treatment with base and loss of the cyano and silyloxy groups.

Recent advances in 4-hydroxycoumarin chemistry. Part 1: Synthesis and reactions

“…N-bromosuccinmide (NBS) is generally utilized for bromination of 4-hydroxycoumarin 1 at room temperature using different catalysts such as polyethylene glycol (PEG-400) (Venkateswarlu et al, 2009), sulfonic-acidfunctionalized silica (Das et al, 2006), ammonium acetate (Das et al, 2007), anhydrous magnesium perchlorate (Zhang et al, 2007) or tetrabutylammonium bromide (TBAB) (Ganguly et al, 2005) (Scheme 98). Ammonium bromide and Oxone® (Kumar et al, 2010) or tetrabutylammomium bromide and phosphorus pentoxide (Jung and Allen, 2009;Kato et al, 2001) have also been used as another brominating agents for this reaction (Scheme 53). When the bromination of 4-hydroxycoumarin 1 is carried out using vanadium pentoxide as an effective promoters with tetrabutylammonium bromide in the presence of hydrogen peroxide, it is afforded α,α-dibromo-2-hydroxyacetophenone 184 (Bora et al, 2000) (Scheme 99).…”

Novel and Efficient One-Step Parallel Synthesis of Dibenzopyranones via Suzuki−Miyaura Cross Coupling

“…The most popular involves Suzuki-Miyaura cross coupling followed by Lewis acid6 or metal7 mediated lactonization. More recently the Diels-Alder cycloaddition of 4-cyanocoumarins,8 tert -butyllithium-mediated cyclization of bromobenzylfluorophenyl ethers,9 and ruthenium-catalysed cyclotrimerization of aryl diynes10 have been reported. In 2002, Abbott Laboratories reported a practicable and scalable synthesis of glucocorticoid receptor A-224817.0 through a Negishi cross coupling 11.…”

Dicyano(7‐methyl‐6‐oxo‐6H‐dibenzo[b,d]pyran‐9‐yl)methanide Salts via a Multicomponent Reaction

“…1, B). Several natural products, including progesterone, androgen, glucocorticoid receptor agonists, and endothelial cell proliferation inhibitors, have been synthesized from these pharmacophores as intermediates [1].…”

“…Cyclization of bromobenzyl fluorophenyl ethers in the presence of (tert- Helvetica Chimica Acta -Vol. 96 (2013) 906 butyl)lithium [3], condensation of resorcinol (¼ benzene-1,3-diol) with substituted 2bromobenzoic acids in alkaline medium in the presence of copper sulfate catalyst (Hurtley reaction) [4], cyclotrimerization of aryldiynes in the presence of a ruthenium catalyst [5], CÀO carboxylic coupling reaction catalyzed by copper(I) salts [6], and a DielsÀAlder reaction between 4-cyanocoumarins (¼ 2-oxo-2H-1-benzopyran-4-carbonitriles) and 1-oxygenated dienes followed by eliminationÀaromatization with KO t Bu [1] are also reported methods for the synthesis of dibenzopyranones. Such existing methods, however, require the use of Pd-catalysts, aryl fluorides and iodides, ionic liquids, or multistep reaction sequences and suffer from disadvantages including low yields, harsh conditions, and expensive reagents.…”

“…of malononitrile (2) with 3-acetylcoumarin (1a). Surprisingly, when the reaction was performed in the presence of piperidine as base under reflux conditions, significant amounts of a polar solid identified as piperidinium dicyano(7-methyl-6-oxo-6H-dibenzo [b,d]pyran-9-yl)methanide (4a) and piperidinium dicyano(3-cyano-4-methyl-5-oxo-5H- [1]benzopyrano [4,3-b]pyridin-2-yl)methanide (3), was isolated from the residue by flash chromatography after evaporation of the solvent (Scheme 1).…”