“…One of the well established events in the oxidation of aldehydes with peracids is the selective formation of carboxylic acids RCO 2 H 5 instead of BVO products (formate esters 4 ), owing to the facile β-elimination of acid ArCO 2 H (or preferential 1,2-shift of hydrogen over the carbon moiety) in Criegee intermediates 1 (Scheme ): , thus, primary aliphatic aldehydes as well as aromatic aldehydes generally produce the corresponding carboxylic acids 5 upon peracid treatment. Oxidation of some α-branched and α-nitrogen-substituted aliphatic aldehydes , as well as electron-rich aromatic aldehydes (Dakin oxidation) is an exception to the general rule and affords formates 4 . We report herein difluoro-λ 3 -bromane-induced BVO of aliphatic and aromatic aldehydes in the presence of water, based on the unique ligand exchange strategy depicted in Scheme b.…”
A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-lambda(3)-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-lambda(3)-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO.
“…One of the well established events in the oxidation of aldehydes with peracids is the selective formation of carboxylic acids RCO 2 H 5 instead of BVO products (formate esters 4 ), owing to the facile β-elimination of acid ArCO 2 H (or preferential 1,2-shift of hydrogen over the carbon moiety) in Criegee intermediates 1 (Scheme ): , thus, primary aliphatic aldehydes as well as aromatic aldehydes generally produce the corresponding carboxylic acids 5 upon peracid treatment. Oxidation of some α-branched and α-nitrogen-substituted aliphatic aldehydes , as well as electron-rich aromatic aldehydes (Dakin oxidation) is an exception to the general rule and affords formates 4 . We report herein difluoro-λ 3 -bromane-induced BVO of aliphatic and aromatic aldehydes in the presence of water, based on the unique ligand exchange strategy depicted in Scheme b.…”
A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-lambda(3)-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-lambda(3)-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO.
“…Formates, formed by migration of the carbon group, are the alternative reaction products, but this rearrangement seldom occurs. In fact, to the best of our knowledge, electron-rich aromatic and heteroaromatic aldehydes and α-oxygen-substituted aldehydes are the main exceptions to the general rule and are converted to formate esters upon peroxy acid treatment. The bizarre behavior of the 2-azetidinone ring, exemplified by different unique transformations, provides a new example of preferential carbon migration on the Baeyer−Villiger rearrangement of aldehydes.…”
Section: Introductionmentioning
confidence: 99%
“…We recently reported 1 that β-lactam aldehydes 1 (Chart ) exclusively yield 4-(formyloxy) β-lactams 2 after Baeyer−Villiger oxidation. This transformation represents one of the scarce examples of the preferred migration of a carbon group in an aliphatic aldehyde. − 1 …”
The Baeyer-Villiger oxidation of 4-formyl-beta-lactams 1with m-CPBA gave 4-(formyloxy) beta-lactams 2 in a simple, efficient, and totally stereoselective process. This reaction is one of the scarce examples of the preferred migration of a carbon moiety in an aliphatic aldehyde. The influence of the substituents at N1 and C3 of the four-membered ring in the Baeyer-Villiger rearrangement has been studied. Thus, alkyl, alkenyl, aryl, and alkyloxy 3-substituted-1-(p-anisyl)-2-azetidinones 1 form exclusively 4-(formyloxy) beta-lactams 2. Amide or acetoxy substituents at C3 of the four-membered ring produce mixtures of 4-(formyloxy) beta-lactams 2and 4-carboxy beta-lactams 5. The exclusive formation of carboxy derivatives is observed sometimes for 1-alkyl-substituted-2-azetidinones 1. 4-(Formyloxy) beta-lactams 2 are suitable starting materials to prepare different 4-unsubstituted beta-lactams 9 using beta-hydroxy amides 8 as isolable intermediates. The overall transformation 4-formyl-2-azetidinone to 4-unsubstituted beta-lactam is an easy and convenient stereoselective route to these interesting types of compounds.
“…As part of our investigations into the Baeyer–Villiger oxidation reactions of α,β-unsaturated ketones, we found that treatment of benzylidene acetone 1 with 4 equiv of m- chloroperoxybenzoic acid ( m -CPBA) in toluene for 24 h gave FAPM ( 5 ) in 84% isolated yield (Scheme a) . In this remarkable one-pot, four-step reaction, benzylidene acetone 1 first undergoes an m -CPBA-mediated Baeyer–Villiger reaction to afford enol acetate 2 , whose electron-rich alkene bond is then epoxidized by a second equivalent of m -CPBA to afford epoxy acetate 3 .…”
Formyloxyacetoxyphenylmethane is a stable, water-tolerant, N-formylating reagent for primary and secondary amines that can be used under solvent-free conditions at room temperature to prepare a range of N-formamides, N-formylanilines, N-formyl-α-amino acids, N-formylpeptides, and an isocyanide.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
