Taking advantage of lithium monohalocarbenoid intrinsic α-elimination in 2-MeTHF: controlled epoxide ring-opening en route to halohydrins

Chemoselective homologative preparation of trisubstituted alkenyl halides from carbonyls and carbenoids

The chemoselective synthesis of trisubstituted alkenyl halides (Cl, Br, F, I) starting from ketones and aldehydes and lithium halocarbenoids is reported. Upon forming the corresponding tetrahedral intermediate adduct, followed by the addition of thionyl chloride, a selective E2-type elimination is triggered, furnishing the targeted motifs. The transformation takes place under full chemocontrol: various sensitive functionalities (e.g. ester, nitrile, nitro, or halogen groups) can be placed on the starting materials, thus documenting a wide reaction scope, as well as the application of the technique to biologically active substances.

Experimental verification of halomethyl carbinol synthesis from carbonyl compounds using a TiCl4-Mg bimetallic complex promoter

A critical evaluation of the feasibility of a previously published method for synthesising halomethyl carbinols from carbonyl compounds and CH2Br2 or CH2Cl2 using a bimetallic TiCl4-Mg complex is presented. The synthesis of compounds lacking the -CH2- group in their structure was achieved by following the procedures proposed in the reference literature or by introducing modifications to selected process parameters. These compounds were not identified as expected β-halohydrins but as products of reductive dimerisation or subsequent pinacolic rearrangement of carbonyl substrates. This paper proposes a formation mechanism of vicinal 1,2-diols in the presence of a TiCl4-Mg system, supported by experimental data and theoretical DFT calculations (DFT/B3LYP).

Highly chemoselective homologative assembly of the α-substituted methylsulfinamide motif from N-sulfinylamines

α-Substituted methylsulfinamide are prepared through the homologation of electrophilic N-sulfinylamines with Li-CHXY reagents. The transformation takes place under full chemocontrol and exhibits good flexibility for preparing both N-aryl and N-alkyl analogues. Various sensitive functionalities can be accommodated on the starting materials, thus documenting a wide reaction scope.

Replacement of Less-Preferred Dipolar Aprotic and Ethereal Solvents in Synthetic Organic Chemistry with More Sustainable Alternatives

Dipolar aprotic and ethereal solvents comprise just over 40% of all organic solvents utilized in synthetic organic, medicinal, and process chemistry. Unfortunately, many of the common "go-to" solvents are considered to be "less-preferable" for a number of environmental, health, and safety (EHS) reasons such as toxicity, mutagenicity, carcinogenicity, or for practical handling reasons such as flammability and volatility. Recent legislative changes have initiated the implementation of restrictions on the use of many of the commonly employed dipolar aprotic solvents such as dimethylformamide (DMF) and N-methyl-2-pyrrolidinone (NMP), and for ethers such as 1,4-dioxane. Thus, with growing legislative, EHS, and societal pressures, the need to identify and implement the use of alternative solvents that are greener, safer, and more sustainable has never been greater. Within this review, the ubiquitous nature of dipolar aprotic and ethereal solvents is discussed with respect to the physicochemical properties that have made them so appealing to synthetic chemists. An overview of the current legislative restrictions being imposed on the use of dipolar aprotic and ethereal solvents is discussed. A variety of alternative, safer, and more sustainable solvents that have garnered attention over the past decade are then examined, and case studies and examples where less-preferable solvents have been successfully replaced with a safer and more sustainable alternative are highlighted. Finally, a general overview and guidance for solvent selection and replacement are included in the Supporting Information of this review.

Fast Addition of s-Block Organometallic Reagents to CO2 -Derived Cyclic Carbonates at Room Temperature, Under Air, and in 2-Methyltetrahydrofuran

Fast addition of highly polar organometallic reagents (RMgX/RLi) to cyclic carbonates (derived from CO₂ as a sustainable C1 synthon) has been studied in 2-methyltetrahydrofuran as a green reaction medium or in the absence of external volatile organic solvents, at room temperature, and in the presence of air/moisture. These reaction conditions are generally forbidden with these highly reactive main-group organometallic compounds. The correct stoichiometry and nature of the polar organometallic alkylating or arylating reagent allows straightforward synthesis of: highly substituted tertiary alcohols, β-hydroxy esters, or symmetric ketones, working always under air and at room temperature. Finally, an unprecedented one-pot/two-step hybrid protocol is developed through combination of an Al-catalyzed cycloaddition of CO₂ and propylene oxide with the concomitant fast addition of RLi reagents to the in situ and transiently formed cyclic carbonate, thus allowing indirect conversion of CO₂ into the desired highly substituted tertiary alcohols without need for isolation or purification of any reaction intermediates.