Synthesis of Chroman-2-ones by Reduction of Coumarins

Abstract

C h r o m a n -2 -o n e s b y R e d u c t i o n o f C o u m a r i n sAbstract: The scientific literature detailing the synthesis of chroman-2-ones by hydrogenation/reduction of the corresponding coumarins is reviewed. The following methods are described: hydrogenation on palladium, platinum, nickel, catalytic transfer hydrogenation, homogeneous hydrogenation, reduction by complex hydrides, reduction by metals, and electrochemical reduction. For each appropriate reaction, the yield, duration and some additional information is given (if available). Moreover, many exceptions and interesting transformations are described.

Asymmetric Synthesis of 4‐Amino‐4H‐Chromenes by Organocatalytic Oxa‐Michael/Aza‐Baylis–Hillman Tandem Reactions

“…[8] At this point we reasoned that reactions of N-activated 2-hydroxy benzaldimines with alkynals would afford 4-amino-4H-chromenes E (Scheme 2c), which could retain the stereochemical information associated to the nitrogen function and could be used as precursors of B by reduction. [9] To the best of our knowledge, this transformation involving an oxa-Michael/aza-Baylis-Hillman (aza-BH) [10] tandem process [11] with alkynals has never been reported and prompted us to study it.The classic aza-BH reaction [10a] consists of the reaction of a nucleophile (usually a catalyst) with a deactivated double bond and further addition of the resulting a-stabilized carbanion to a C=N bond, being finally the catalyst recovered after elimination (Scheme 2a). The use of deactivated triple bonds as electrophiles in aza-BH determines that the final elimination cannot take place (Scheme 2b).…”

“…[8] At this point we reasoned that reactions of N-activated 2-hydroxy benzaldimines with alkynals would afford 4-amino-4H-chromenes E (Scheme 2c), which could retain the stereochemical information associated to the nitrogen function and could be used as precursors of B by reduction. [9] To the best of our knowledge, this transformation involving an oxa-Michael/aza-Baylis-Hillman (aza-BH) [10] tandem process [11] with alkynals has never been reported and prompted us to study it.…”

Aldo‐X Bifunctional Building Blocks for the Synthesis of Heterocycles

“…Coumarin and chromene derivatives are important heterocycles that are often used as drug components, and some of them are also useful for materials chemistry and biology . The synthesis of coumarins from salicylaldehydes is well known.…”

Shikimic Acid Pathway

“…Reduction The coumarin double bond (at C3, C4) undergoes reduction under various conditions to give chroman-2-ones on which a review [36] has recently appeared. A few methods have been mentioned briefly in Sect.…”