Gurunath Suryavanshi

Fluoride-Assisted Synthesis of 1,4,5,6-Tetrahydropyridazines via [4 + 2] Cyclodimerization of in Situ-Generated Azoalkenes Followed by a C–N Bond Cleavage

An unexpected CsF-assisted C-N bond cleavage was exploited to synthesize highly functionalized and biologically important 1,4,5,6-tetrahydropyridazine derivatives from α-halo N-acylhydrazones in excellent yields. The extrusion of nitrogen and the [4 + 2] cycloaddition between in situ-generated azoalkenes is a key reaction in the process. The identified methodology is suitable for synthesizing a wide variety of analogues of tetrahydropyridazines, which are prevalent in many medicinally important small molecules. The reaction conditions are mild, high-yielding, and amenable for the gram scale.

A short enantioselective synthesis of 3-epi-jaspine B and (+)-oxybiotin via an intramolecular tandem desilylation oxa-Michael addition strategy

A new synthesis of cytotoxic anhydrophytosphingosine 3-epi-jaspine B (34.7% overall yield; 97% ee) and (+)-oxybiotin (21.2% overall yield; 97% ee), bioactive oxygen analogue of biotin, is described starting from commercially available cis-2-butene-1,4-diol. The key reactions employed in the synthesis include Sharpless asymmetric epoxidation and a novel tandem desilylation oxa-Michael addition reaction strategy to construct a tetrahydrofuran core (dr >99%).

Diastereoselective Synthesis of Chiral 2,3-Disubstituted Indolines via Formal [3+2]-Cycloaddition of Arynes with γ-Amino-α,β-unsaturated Esters

A one step formal [3+2]-annulation protocol for the synthesis of 2,3-disubstituted indolines is described. The in situ generated aryne acts as a two-atom component, and γ-amino-α,β-unsaturated esters acting as a three-atom component to construct indoline units in a highly regio- and diastereoselective manner with yields ranging from 63 to 80%.

Synthesis of key intermediate for (+)-tofacitinib through CoIII(salen)-catalyzed two stereocentered hydrolytic kinetic resolution of (±)-methyl-3-(oxiran-2-yl)butanoate

ABSTRACT An enantiopure piperidine, a key intermediate for the synthesis of (+)-tofacitinib, has been achieved in high optical purity (98% ee) from readily available crotyl alcohol. The key steps involved is a CoIII(salen)-OAc-catalyzed two stereocentered hydrolytic kinetic resolution of (±)-methyl-3-(oxiran-2-yl)butanoate. GRAPHICAL ABSTRACT

Metal-free annulation of β-acylamino ketones: facile access to spirooxazolines and oxazolines via oxidative C–O bond formation

A metal-free annulation reaction of β-acylamino ketone derivatives has been reported for the synthesis of a group of functionalized spirooxazolines and oxazolines in good to excellent yields. The reaction proceeds via phenyliodine(III) diacetate (PIDA)-mediated oxidative C–O bond formation in the presence of BF3–OEt2. The mild reaction conditions, broad substrate scope, simple execution and synthetic potential of the products make this novel protocol very attractive.

Metal-free hypervalent iodine/TEMPO mediated oxidation of amines and mechanistic insight into the reaction pathways

A highly efficient metal free approach for the oxidation of primary and secondary amines to their corresponding aldehydes and ketones using PhI(OAc)2 in combination with a catalytic amount of TEMPO as an oxidizing agent is described. This protocol is rapid and provides diverse products under milder reaction conditions in excellent yields. In addition, the mechanistic study is well demonstrated by spectroscopic methods.

Two stereocentered HKR of anti-β,β′-diphenylpropanoxirane and anti-3-phenylethyloxiranes catalysed by Co(III)(salen)-OAc complex: enantioselective synthesis of (+)-sertraline and (+)-naproxen

The Co(III)(salen)OAc-catalyzed two stereocentered hydrolytic kinetic resolution (HKR) of anti-β,β′-diphenylmethyloxirane and anti-3-phenylethyloxiranes affords the corresponding anti-1,2-diols and oxiranes in high enantiomeric excess. The synthetic potential of this methodology is demonstrated by the enantioselective synthesis of (+)-sertraline, an antidepressant drug, and (+)-naproxen, an anti-inflammatory drug.

Triflic acid-catalyzed metal-free synthesis of (E)-2-cyanoacrylamides and 3-substituted azetidine-2,4-diones

A TfOH-catalyzed highly efficient synthesis of biologically active (E)-2-cyanoacrylamides and 3-substituted azetidine-2,4-diones has been reported with 64–94% yields under metal-free conditions. The reaction proceeds through sequential Knoevenagel condensation/stereoselective in situ monohydration of nitrile or C–N cyclization protocol in one-pot. The attractive features of this tandem process are moderate reaction conditions, high atom economy, broad substrate scope, gram-scale reaction and ease of operation.