Retro Diels Alder protocol for regioselective synthesis of novel [1,2,4]triazolo[4,3-a]pyrimidin-7(1H)-ones

Reactions of diastereochemically varied norbornene-condensed 2-thioxopyrimidin-4-ones 6 and 10 with variously functionalized hydrazonoyl chlorides 2a-h gave regioselectively angular norbornene-based [1,2,4]triazolo[4,3-a]pyrimidin-7(1H)-ones 7a-h and 11a,c-e, respectively. Thermal retro Diels-Alder (RDA) reaction of 7a-h and 11a,c-e resulted in the target compounds 4a-h as single products. On the other hand, reactions of thiouracil 1 and hydrozonoyl chlorides 2a-e gave regioselectively [1,2,4]triazolo[4,3-a]pyrimidinone-5(1H)-ones 3a-e. The opposite regioselectivity of thiouracil 1 and norbornene-condensed 2-thioxopyrimidin-4-ones 6 and 10 was attributed to electronic factors according to DFT calculations. The angular structure of norbornene based [1,2,4]triazolo[4,3-a]pyrimidin-7(1H)-ones was confirmed by single crystal X-ray crystallography.

Green synthesis and characterisation of novel [1,3,4]thiadiazolo/benzo[4,5]thiazolo[3,2-a]pyrimidines via multicomponent reaction using vanadium oxide loaded on fluorapatite as a robust and sustainable catalyst

We synthesised materials with different loadings of vanadia on fluorapatite (V2O5/FAp), fully characterised their structural properties using various spectral techniques including TEM, BET, XRD, FT-IR, SEM and EDX and assessed their prowess as catalysts. The 2.5% V2O5/FAp exhibited excellent activity for the synthesis of novel [1,3,4]thiadiazolo[3,2-a]pyrimidines and benzo[4,5]thiazolo[3,2-a]pyrimidines. The one-pot three-component fusion reaction between chosen substrates of 1,3,4-thiadiazole-amines or 2-amino-benzothiazole, aldehydes and active methylene compounds in ethanol solvent at room temperature gave an excellent yield of products (90-97%) in a swift reaction (25-30 min). The advantages of this protocol are rapid synthesis, mild reaction conditions, green solvent, easy work-up, eco-friendliness, reusability of catalyst and no need for column chromatography.

Synthesis of 2-arylated thiadiazolopyrimidones by Suzuki–Miyaura cross-coupling: a new class of nucleotide pyrophosphatase (NPPs) inhibitors

Over expression of nucleotide pyrophosphatase (NPPs) activity is associated with chondrocalcinosis, osteoarthritis, type 2 diabetes, neurodegenerative diseases, allergies and cancer metastasis.

Convenient and efficient synthesis of disubstituted piperazine derivatives by catalyst-free, atom-economical and tricomponent domino reactions

One-pot, atom-economical, catalyst-free and tri-component domino reactions are applied to diversity-oriented synthesis (DOS) of disubstituted piperazine derivatives under mild conditions with moderate to high yields.