Advancing Air‐ and Moisture‐Compatible s‐Block Organometallic Chemistry Using Sustainable Solvents

Abstract

Challenging conventional wisdom that s-block organometallic reagents such as Grignard or organolithiums need to be used under protecting inert atmosphere (N 2 or Ar), employing dry organic solvents with a strict temperature control, this Minireview focusses on recent advances on the use of these commodity reagents while operating under air, at room temperature and in the presence of moisture. Key for the success of these approaches has been the use of the following sustainable solvents: i) water; ii) Deep Eutectic Solvents (DESs); or iii) biomass-derived polyols (like glycerol) or ethereal solvents [i. e., 2-MeTHF or cyclopentyl methyl ether (CPME)]. The versatility of these air and moisture compatible synthetic protocols has been demonstrated for a myriad of key organic transformations, including nucleophilic additions of RLi/RMgX reagents to unsaturated organic molecules (i. e., ketones, imines, esters, amides or nitriles) as well as ortho-and lateral lithiation of aromatic substrates, Pd catalysed cross-couplings and anionic polymerisation of styrenes. Extension of these studies to lithium amides (LiNR 2 ) or phosphides (LiPPh 2 ) has enabled the development of more sustainable and efficient methods for CÀ N and CÀ P bond forming processes. These unconventional s-block metal mediated transformations have also been successfully incorporated in one-pot tandem processes in combination with transition-metal and organo-catalysis. Remarkably, in some cases the conversions and chemoselectivities observed are superior to those detected in common toxic organic solvents, while working under inert atmosphere conditions with strict temperature control. The key role played by the choice of solvent in these transformations and how it can affect the constitution of the s-block organometallic species present in solution is also discussed.

Sustainable Pd-Catalyzed Direct Arylation of Thienyl Derivatives with (Hetero)aromatic Bromides under Air in Deep Eutectic Solvents

“…Furthermore, taking advantage of some peculiar properties like high viscosity, conductivity, and polarity, as well as high solubility in water, which usually simplify the isolation of the final products, DESs have been successfully employed as alternatives to VOCs in many organic and organometallic transformations. − For example, the employment of polar organometallic reagents like alkyl- and aryllithium species , in DESs has been successfully proven under mild conditions and very short reaction times. A very important class of transformations that were positively affected by the use of DESs consist of cross-coupling reactions, as reported for Suzuki–Miyaura, − Sonogashira, ,, Hiyama, , Negishi, Stille–Migita, and Ullmann-type − reactions, which have been extensively investigated in recent years.…”

Deep Eutectic Solvents in Solar Energy Technologies

“…All of these exceptional features, combined with the low cost of components, easiness of preparation with high purity, high biodegradability and low toxicity, have made DESs attractive and promising as a new generation of nonaqueous solvents/cosolvents for a broad range of applications in organic synthesis [ 24 , 25 , 26 ], main group chemistry [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], metal-, bio-, and organo-catalysis [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ], dissolution and extraction processes [ 54 , 55 , 56 , 57 , 58 ], electrochemistry [ 59 , 60 ], material chemistry [ 61 , 62 ], photosynthesis [ 63 ], and even protein crystallization [ 64 ].…”

Reusable Deep Eutectic Solvents for Clean ε-Caprolactam Synthesis under Mild Conditions

“…28,29 Among them, choline chloride was often used to produce DESs because of its excellent biocompatibility, Brønsted acidic characteristics (which can provide Brønsted acid center site for the acid catalyzed reaction), and thermal stability. 30,31 DESs have recently attracted increasing interest particularly in a wide variety of green chemistry, 32−34 including separation, 35 material chemistry, 36 electrochemistry, 37 chemical catalysis, 38 biocatalysis, 39 main-group organometallic chemistry, 40 and solubility, 41,42 especially in organic synthesis. 43 As a new green solvent, DESs show good application prospects as reaction media or catalysts in organic synthesis.…”

“…DESs have recently attracted increasing interest particularly in a wide variety of green chemistry, − including separation, material chemistry, electrochemistry, chemical catalysis, biocatalysis, main-group organometallic chemistry, and solubility, , especially in organic synthesis . As a new green solvent, DESs show good application prospects as reaction media or catalysts in organic synthesis.…”