Bismuth(III) triflate catalyzed tandem esterification–Fries–oxa-Michael route to 4-chromanones

Abstract

An efficient tandem reaction approach is described to prepare 4-chromanones from electron-rich phenols and 3,3-dimethylacrylic acid or trans-crotonic acid in boiling toluene using 20 mol% bismuth(III) triflate as the catalyst. The reaction is also successful from the corresponding aryl esters of each of these acids under the same conditions. The procedure is convenient to perform, and 25-90% yields of products are realized following chromatography. A range of substrates is included (14 substrates for each acid) to help define the scope of the process. Additional experiments are reported, which confirm that the sequence of events involves (1) esterification, (2) Fries rearrangement and (3) oxa-Michael ring closure.

Allyl‐Palladium‐Catalyzed α,β‐Dehydrogenation of Carboxylic Acids via Enediolates

“…In addition, readily available enoic acids could undergo decarboxylative coupling with β‐bromostyrenes under palladium catalysis to produce the corresponding butadiene derivatives ( 3 c ), which are commonly seen in a number of bioactive compounds and materials. Furthermore, fused‐ring systems such as 4‐chromanone ( 3 d ) and indanone ( 3 e ) were also obtained through annulation by Michael addition and Friedel–Crafts acylation.…”

Bismuth(III) triflate: An Efficient Catalyst for the Synthesis of Diverse Biologically Relevant Heterocycles

“…Meraz et al . (Table ) reported a simple, convenient, bismuth(III) triflate catalyzed efficient tandem reaction protocol for the synthesis of a series of 4‐chromanones ( 50 ) (28 entries) from electron‐rich phenols ( 46 ) and 3,3‐dimethylacrylic acid ( 47 ) or trans‐crotonic acid ( 48 ) in toluene under reflux condition. Under the same optimized condition the corresponding aryl esters ( 49 ) are also gave the desired products in good to excellent yields.…”

Allyl‐Palladium‐Catalyzed α,β‐Dehydrogenation of Carboxylic Acids via Enediolates

“…Decarboxylative coupling reactions are also feasible as in the case of the rhodium-catalyzed directed C À Ho lefination to form 3b (Figure 2b). [19] In addition, readily available enoic acids could undergo decarboxylative coupling [20] with bbromostyrenes under palladium catalysis to produce the corresponding butadiene derivatives (3c), [21] which are commonly seen in an umber of bioactive compounds and materials.Furthermore,fused-ring systems such as 4-chromanone (3d) [22] and indanone (3e) [23] were also obtained through annulation by Michael addition and Friedel-Crafts acylation.…”