Anil M. Shelke

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%).

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.

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.