IBX/LiBr-promoted one-pot oxidative anti-Markownikov bromohydroxylation/bromoalkoxylation of Baylis–Hillman olefins

Mechanistic Investigations on the Interaction of Morita-Baylis-Hillman Ketones with 2-Aminothiophenol

The reaction of Morita-Baylis-Hillman ketones with 2-aminothiophenol mediated by Cs2CO3 results in an oxidative cyclization to 2,2-disubstituted dihydro-1,4-benzothiazines, with the structure of the product indicating the occurrence of an aza-Michael addition along the pathway. In contrast, in the absence of a base, the parent compounds interact to produce a thia-Michael adduct instead. A deeper mechanistic study improved our understanding of the apparent contradiction and provided insight into the base-dependent switch in reactivity.

Acyl Transfer-Driven Rauhut-Currier Dimerization of Morita-Baylis-Hillman Ketones

A serendipitous Rauhut-Currier dimerization of 1,1-disubstituted activated olefins derived from Morita-Baylis-Hillman adducts was observed in the presence of DABCO. The reaction is driven by the migration of an acyl group and produces multifunctionalized enol esters in yields greater than 90% in most cases, without necessitating column chromatographic purification. The acyl transfer is thought to proceed via a transition state typical of a Morita-Baylis-Hillman (MBH) reaction, supported by a brief mechanistic study involving computational calculations.

Synthesis of 2,2-Disubstituted Dihydro-1,4-benzothiazines from Morita-Baylis-Hillman Ketones by an Oxidative Cyclization

An oxidative cyclization ensued upon interaction of Morita-Baylis-Hillman (MBH) ketones with 2-aminothiophenol in the presence of Cs₂CO₃, resulting in the formation of new 2,2-disubstituted dihydro-1,4-benzothiazines. The reaction features an aza-Michael addition and an oxidative cyclization involving the formation of a carbon-sulfur bond and works well over a wide range of MBH ketones to deliver the dihydrobenzothiazines in good yields in reasonable reaction times under mild conditions.

Diamine-mediated degradative dimerisation of Morita-Baylis-Hillman ketones

A degradative dimerisation of Morita-Baylis-Hillman ketones was observed in the presence of a primary diamine. The reaction proceeded swiftly to produce methylene-bridged 1,3-dicarbonyl compounds. A brief mechanistic investigation alluded to a retro-Mannich reaction as the key step of the transformation.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

Organoiodine(V) reagents in organic synthesis

Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.