Amine-Controlled Divergent Reaction: Iminolactonization and Olefination in the Presence of a Cu(I) Catalyst

α-Halocarbonyls as a Valuable Functionalized Tertiary Alkyl Source

This review introduces the synthetic organic chemical value of α-bromocarbonyl compounds with tertiary carbons. This α-bromocarbonyl compound with a tertiary carbon has been used primarily only as a radical initiator in atom transfer radical polymerization (ATRP) reactions. However, with the recent development of photo-radical reactions (around 2010), research on the use of α-bromocarbonyl compounds as tertiary alkyl radical precursors became popular (around 2012). As more examples were reported, α-bromocarbonyl compounds were studied not only as radicals but also for their applications in organometallic and ionic reactions. That is, α-bromocarbonyl compounds act as nucleophiles as well as electrophiles. The carbonyl group of α-bromocarbonyl compounds is also attractive because it allows the skeleton to be converted after the reaction, and it is being applied to total synthesis. In our survey until 2022, α-bromocarbonyl compounds can be used to perform a full range of reactions necessary for organic synthesis, including multi-component reactions, cross-coupling, substitution, cyclization, rearrangement, stereospecific reactions, asymmetric reactions. α-Bromocarbonyl compounds have created a new trend in tertiary alkylation, which until then had limited reaction patterns in organic synthesis. This review focuses on how α-bromocarbonyl compounds can be used in synthetic organic chemistry.

Copper-catalyzed intramolecular iminolactonization cyclization reactions of remote C(sp3)–H bonds in carboxamides

A novel and efficient synthetic method for iminolactones by copper-catalyzed intramolecular C(sp3)–H bond functionalization of carboxamides via a cascade process is reported for the first time.

Copper-catalyzed aerobic double functionalization of benzylic C(sp3)-H bonds for the synthesis of 3-hydroxyisoindolinones

A copper-catalyzed aerobic 3-hydroxyisoindolinone synthesis was developed via the benzylic double C(sp³)-H functionalization of 2-alkylbenzamides. In this reaction, molecular oxygen was used as both an oxidant for C(sp³)-H functionalization and an oxygen source. Our method can be extended to diverse benzylic C(sp³)-H bonds and shows excellent functional group tolerance.

Cobalt-catalyzed annulation of styrenes with α-bromoacetic acids

We report a method for addition of α-bromophenylacetic acids to vinyl C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds in styrenes to afford γ-lactones. Reactions employed a simple cobalt catalyst Co(NO₃)₂·6H₂O in the presence of dipivaloylmethane (dpm) ligand. Many functionalities including halogen, ester, and nitro groups were compatible with reaction conditions. If α-bromoesters were used, vinylacetates were the major products.

Cobalt-catalyzed addition of α-bromoacetic acids/acetates to CC bonds in styrenes is reported for the first time. Good tolerance of functional groups was observed.

Three-Component Iminolactonization Reaction via Bifunctionalization of Olefins Using Molecular Iodine and Visible Light

A novel three-component γ-iminolactonization reaction was developed, which relied on the C-C/C-O bond-forming bifunctionalization of olefins using molecular iodine and visible light. This strategy did not require any (heavy) metal reagents for double-bond activation because molecular iodine acted as a rare-metal-alternative reagent through visible light irradiation. In addition, the preactivation of amines and other substrates is not required. The mechanistic investigation revealed that the generated iodine radicals under visible light irradiation reacted with alkenes to form a highly reactive intermediate; then, the three-component reaction of diiodide, malonate, and amine furnished iminolactone. Of note, the developed reaction is simple and realized the diversity-oriented synthesis innovative methodology of γ-iminolactone derivatives in drug discovery chemistry.

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C-N, C-O and C-S bond forming reactions, and later widely employed in C-C cross-coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.

Transition-Metal-Catalyzed Alkyl Heck-Type Reactions

The Heck reaction is one of the most reliable and useful strategies for the construction of C-C bonds in organic synthesis. However, in contrast to the well-established aryl Heck reaction, the analogous reaction employing alkyl electrophiles is much less developed. Significant progress in this area was recently achieved by merging radical-mediated and transition-metal-catalyzed approaches. This review summarizes the advances in alkyl Heck-type reactions from its discovery early in the 1970s up until the end of 2018.

Regioselective Synthesis of γ-Lactones by Iron-Catalyzed Radical Annulation of Alkenes with α-Halocarboxylic Acids and Their Derivatives

An abundant and low toxicity iron catalyst has enabled regioselective annulation of alkenes with α-halocarboxylic acids and their derivatives. The reaction proceeds smoothly without any additional ligands, bases, and additives to afford a variety of γ-lactones in good yields. A proposed reaction pathway through radical annulation is supported by some mechanistic studies, involving radical clock and isotope labeling experiments. The present method was applied to the practical iron-powder-promoted synthesis of γ-lactones.

Copper-catalyzed formylation of alkenyl C-H bonds using BrCHCl2 as a stoichiometric formylating reagent

The first example of copper-catalyzed direct formylation of alkenyl C-H bonds for the facile synthesis of α,β-unsaturated aldehydes has been developed. This transformation has demonstrated high reactivity, mild reaction conditions and a broad substrate scope. BrCHCl2 is expected to be developed as an efficient stoichiometric C1 building block in organic synthesis.

Cu-catalyzed intermolecular oxyalkylation of styrenes under air: access to diverse iminolactones

A practical, simple, and efficient copper-catalyzed oxyalkylation of styrenes with α-bromoacetamides for the synthesis of iminolactones was developed under air.