Biocatalysis integrate microbiologists, enzymologists, and organic chemists to access the repertoire of pharmaceutical and agrochemicals with high chemoselectivity, regioselectivity, and enantioselectivity. The saturation of carbon-carbon double bonds by biocatalysts challenges the conventional chemical methodology as it bypasses the use of precious metals (in combination with chiral ligands and molecular hydrogen) or organocatalysts. In this line, Enereductases (ERs) from the Old Yellow Enzymes (OYEs) family are found to be a prominent asymmetric biocatalyst that is increasingly used in academia and industries towards unpar-alleled stereoselective trans-hydrogenations of activated C=C bonds. ERs gained prominence as they were used as individual catalysts, multi-enzyme cascades, and in conjugation with chemical reagents (chemoenzymatic approach). Besides, ERs' participation in the photoelectrochemical and radical-mediated process helps to unlock many scopes outside traditional biocatalysis. These up-and-coming methodologies entice the enzymologists and chemists to explore, expand and harness the chemistries displayed by ERs for industrial settings. Herein, we reviewed the last five year's exploration of organic transformations using ERs.

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A straight-forward and practical metal-free amidation and transesterification of esters have been exemplified in this protocol. This strategic reaction features mild bases and devoid of additives at a reasonable temperature (55°C). The wide range of amines including aromatic amines, was successfully subjected to amidation that supplements the scope exploration. Likewise, various transesterification products from alcohols were realized under this optimized condition. Scheme 1. Coupling reaction of activated esters-AC (a-c) and unactivated esters-UAC (d) with nucleophiles and our work (e).

A straightforward protocol to acylate oxindoles using methyl and phenyl esters mediated by LiHMDS and KOtBu respectively via the mixed Claisen condensation under mild reaction conditions.

Ketones are the key functional group that recurs in chemistry and biology, and accessing them through simple and economic ways is highly desirable. Herein, we report the synthesis of unsymmetrical ketones from abundant toluene and alkyl esters, where volatile alcohols are the sole byproduct. This protocol applies to a repertoire of substrates bearing electron-donating, electron-withdrawing, and neutral substituents. Most importantly, the organometallic ferrocenyl ester underwent aroylation with ease. This method is the first example to furnish diketones from methyl arenes and diesters. Furthermore, cyclic imide was synthesized by this protocol utilizing KN(SiMe 3 ) 2 as a 'nitrogen' source. Density functional theory studies provide insight into deprotonation of toluene by K + -π interaction by increasing its acidity, and this being the rate-determining step.

Topologically constrained naphthalimide appended Pd-NHCs were synthesized and characterized. These structurally related complexes were catalytically compared with previously synthesized Pd-NHCs in the regioselective heteroannulation of o-haloanilines and arylethynyl-trimethylsilane. The unique effect of an additive on product selectivity has been clearly demonstrated. The scope of the reaction with respect to different TMS protected alkynes and o-haloanilines is presented. Importantly, the step-economical regioselective synthesis of N-alkyl-3-aryl-indoles from o-haloanilines and arylethynyl-trimethylsilane assisted by Pd(ii)-NHCs has been clearly demonstrated via one-pot heteroannulation, TMS deprotection and N-alkylation. In addition, synthetic utility was demonstrated with several derivatizations.

The activation and functionalization of the benzylic CH bond by transition metal catalysts have gathered much attraction owing to their occurrence in agrochemicals, pharmaceuticals, and fine chemicals. Among the various active metal catalysts, ruthenium gained upper hand, as they are comparatively economic as well as show versatile catalytic activity. Ruthenium efficiently activates the benzylic C(sp 3 )H bond and effects alkylation, arylation, allylation, vinylation, cyanation, silylation, amination, amidation, and oxidation reactions.

α-Branched amines are key motifs that exist in a plethora of natural products and pharmaceuticals. Herein we disclose the first convergent synthesis of α-branched amines bearing β-carbonyl in isoindolinones by employing unactivated tertiary amides and unactivated alkyl esters as benign electrophile sources. The reaction proceeds by the direct aroylation of a C(sp 3)–H carbon adjacent to the nitrogen atom in core isoindolinones. Several amides and esters were screened to choose the potential acyl source for the substrate scope. The reaction is carried out with a repertoire of substrates under mild conditions and shows high functional group compatibility. Remarkably the reaction is amenable to organometallic ferrocenyl ester and indole methyl esters bearing an acidic NH moiety. Strikingly no trace of amidation product 8 is observed. In particular α-branched amines bearing β-carbonyl synthesized from indole methyl esters are considered important targets, as both motifs are prevalent in many drugs. This protocol is scalable, and products obtained from indole methyl esters show strong solid-state emission properties which are complementary with DFT calculations.