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The pyrolysis of Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) 1 derivatives in solution and in the gas-phase takes place by loss of acetone and carbon dioxide to provide ketene intermediates. In particular, methylene Meldrum's acid derivatives 7 often provide methyleneketenes 8, which act as substrates for internal hydrogen transfer leading to cyclisation reactions. The availability of versatile synthetic routes to 7 (in particular R = heteroatom) has led to the efficient preparation of a diverse range of cyclic compounds such as quinolinones, 3-hydroxythiophenes, naphthols, azepin-3(2H)-ones or pyrrolizin-3-ones initiated respectively by 1,3-1,4-1,5-1,6-or 1,7-prototropic shifts. These reactions are discussed in the context of a rigorous understanding of the chemistry of the ketene intermediates involved. Most of the work was published in the period 1980-2000 but important references to earlier literature are also included.

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Targeting the epidermal growth factor receptors (EGFRs) with small inhibitor molecules has been validated as a potential therapeutic strategy in cancer therapy. Pyrazolo[3,4‐d]pyrimidine is a versatile scaffold that has been exploited for developing potential anticancer agents. On the basis of fragment‐based drug discovery, considering the essential pharmacophoric features of potent EGFR tyrosine kinase (TK) inhibitors, herein, we report the design and synthesis of new hybrid molecules of the pyrazolo[3,4‐d]pyrimidine scaffold linked with diverse pharmacophoric fragments with reported anticancer potential. These fragments include hydrazone, indoline‐2‐one, phthalimide, thiourea, oxadiazole, pyrazole, and dihydropyrazole. The synthesized molecules were evaluated for their anticancer activity against the human breast cancer cell line, MCF‐7. The obtained results revealed comparable antitumor activity with that of the reference drugs doxorubicin and toceranib. Docking studies were performed along with EGFR‐TK and ADMET profiling studies. The results of the docking studies showed the ability of the designed compounds to interact with key residues of the EGFR‐TK through a number of covalent and noncovalent interactions. The obtained activity of compound 25 (IC50 = 2.89 µM) suggested that it may serve as a lead for further optimization and drug development.

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The thermal decomposition of the ferric and nickel acetate salts has been followed. It was found that the heating rate affects the decomposition steps. For a heating rate of 1 K min -I the product is either Fe203 or NiO. For a higher heating rate the suboxides are obtained and reoxidized again on further heating. The decomposition of the mixed salt is an overlap of the DTA for the separate salts but the decomposition reactions are shifted to lower temperatures.