Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

The increasing synthetic utility of allenes in organic synthesis combined with their incorporation into a growing list of natural products and active pharmaceutical ingredients has stimulated an intense effort recently to identify efficient catalytic methods for their synthesis. In addition, as the only common functional group in organic chemistry that possesses axial chirality, efforts to discover new asymmetric catalysts for the enantioselective synthesis of axially chiral allenes has intensified as these substrates become more ubiquitous as chiral building blocks for downstream asymmetric methodologies. Nonetheless, despite this intensive effort, the ability to access racemic or chiral allenes from readily available starting materials using catalytic processes has yet to meet the demand of their expanding applications. The focus of this Perspective is to provide a critical assessment on the most recent developments in the field of catalytic syntheses of allenes (2011–2013) highlighting both the advanta...

Recent Advances in the Catalytic Syntheses of Allenes: A Critical Assessment

Nitriles and alkenes are important synthetic intermediates with complementary reactivity that play a central role in the preparation of materials, pharmaceuticals, cosmetics, and agrochemicals. Here, we report a nickel-catalyzed transfer hydrocyanation reaction between a wide range (60 examples) of alkyl nitriles and alkenes. This strategy not only overcomes the toxicity challenge posed by the use of HCN in traditional approaches, but also encompasses distinct chemical advances, including retro-hydrocyanation and anti-Markovnikov regioselectivity. In a broader context, this work highlights an approach to the reversible hydrofunctionalization of alkenes through thermodynamically controlled transfer reactions to circumvent the use of volatile and hazardous reagents in the laboratory.

http://science.sciencemag.org/content/sci/351/6275/832.full.pdf

Catalytic reversible alkene-nitrile interconversion through controllable transfer hydrocyanation.

The ring and I: hypervalent iodine compounds avoid the issues of toxicity or complicated ligands of many transition-metal-based systems. A highly enantioselective oxyamination of alkenes with N-sulfonyl ureas employing chiral, lactic acid-based hypervalent iodine reagents gives a facile synthesis of enantiomerically pure 2-arylproline derivatives for the first time.

Highly stereoselective metal-free oxyaminations using chiral hypervalent iodine reagents

The Petasis boron–Mannich reaction, simply referred to as the Petasis reaction, is a powerful multicomponent coupling reaction of a boronic acid, an amine, and a carbonyl derivative. Highly functio...

Reactivity and Synthetic Applications of Multicomponent Petasis Reactions

A one-pot synthesis of allenes by the 2-nitrobenzenesulfonylhydrazide-mediated coupling of hydroxyaldehydes or ketones with alkynyl trifluoroborate salts is reported. This mild process involves in situ formation of a sulfonylhydrazone that reacts with alkynyl trifluoroborates to generate a transient propargylic hydrazide species. Decomposition of this unstable hydrazide via an intermediate monoalkyldiazine produces the allene products through an alkene walk mechanism.

A Direct Synthesis of Allenes by a Traceless Petasis Reaction

Stereoselective synthesis of dienes from N-allylhydrazones.

Allylic hydrazines react with aldehydes and alcohols to afford functionalized ether adducts.

A hypervalent iodide-initiated fragment coupling cascade of N-allylhydrazones.

The development of a stereoselective one-pot oxidative [3,3] sigmatropic rearrangement/Friedel–Crafts arylation that provides enantioenriched benzhydryl compounds is reported. The utility of this new transformation is demonstrated by the concise synthesis of several tetralone- and naphthyl-type lignan natural products, many of which display anti-malarial activity.

Stereocontrolled Syntheses of Tetralone- and Naphthyl-Type Lignans by a One-Pot Oxidative [3,3] Rearrangement/Friedel–Crafts Arylation†

A method is provided for forming a composite coating on a substrate comprising: (A) applying a first coating composition to a surface of the substrate; and (B) applying a second coating composition to the first coating prior to substantially heating or curing the first coating. The first and/or second coating composition is a waterborne curable film-forming composition comprising: (a) an aqueous dispersion of internally crosslinked polymeric microparticles having a core-shell morphology and having reactive functional groups; and (b) a crosslinking agent. The core of the polymeric microparticles is prepared from a monomer mixture comprising at least 20 percent by weight of a monomer having the structure shown in claim 1 wherein X is N or O; R is a linear or branched alkyl group having 1 to 18 carbon atoms, or R is bonded to X to form a 5- to 7-member ring.

Kelly E. Lutz

Papers

A Direct Synthesis of Allenes by a Traceless Petasis Reaction

Stereoselective synthesis of dienes from N-allylhydrazones.

A hypervalent iodide-initiated fragment coupling cascade of N-allylhydrazones.

Stereocontrolled Syntheses of Tetralone- and Naphthyl-Type Lignans by a One-Pot Oxidative [3,3] Rearrangement/Friedel–Crafts Arylation†

Coating processes using waterborne curable film-forming compositions containing polymers derived from natural gas raw materials