Synthesis of β-cyanoalanine and enantiomerically enriched aspartate derivatives via the Zn- or In-mediated nucleophilic addition to α-imino esters

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.

Solvent Effects on Heterogeneous Rate Constants for Indium Mediated Allylations

Indium mediated allylation is a highly selective tool for synthetic chemists to create carbon-carbon bonds, but the first step, heterogeneous reaction of allyl halides at solid indium surfaces, is still poorly understood. For example, the nature of the solvent dramatically affects the rate of reaction, but solvent choice is often based on empirical experiments. Fundamental kinetic studies are the best way to study this effect, but the determination of heterogeneous rate constants is challenging. In an effort to better understand solvent effects, we use optical microscopy to determine heterogeneous rate constants for IMA in aqueous acetonitrile, methanol, ethanol, and 2-propanol. We fit the reaction rate data over a range of mass transport rates using only two adjustable parameters, the heterogeneous rate constant and the mass transport rate. The results emphasize the critical importance of water in determining the rate of reaction. Surprisingly, the polarity of the organic solvent in the mix does not have a major effect on the rate. It is hypothesized that the oxygen atom in water and alcohols is an especially effective Lewis base to stabilize the transition state and the organoindium intermediates, similar to the importance of the oxygen in ethers for the formation of Grignard reagents. This study again demonstrates the power of microscopy for the study of heterogeneous reactions.