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A series of pentasubstituted 4H-pyrans and tetrahydrobenzo[b]pyrans are synthesized with excellent yields via a one-pot condensation of aromatic aldehydes, malononitrile, and a dicarbonyl compound, ethyl acetoacetate, acetyl-acetone or dimedone, in the presence of 4 Å molecular sieve modified with zinc(II) as heterogeneous catalyst, in ethanol. The process offers numerous advantages, such as better yield, short reaction time, and mild reaction conditions. The catalyst’s preparation is simple and it could be reused while still maintaining its activity.

In this review the most important results achieved in the recent 12--15 years are summarized focusing on the heterogenous catalytic hydrogenations over transition metals (Pd, Pt, Ru, Rh, La), as well as the application of palladium, copper and other metals on a molecular sieve (4A) support in several organic chemical syntheses in liquid phase. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed cross-coupling of organo-halides, ethers, sulfides, amines, and alcohols (and derivatives thereof) with Grignard reagents, known as the Kumada–Tamao–Corriu reaction, can be used to prepare important intermediates in the synthesis of numerous- biologically active compounds. The most frequently used transition metals are nickel, palladium, and iron, but there are several examples for cross-coupling reactions catalyzed by copper, cobalt, manganese, chromium, etc. salts and complexes. The aim of this review is to summarize the most important transition-metal-catalyzed cross-coupling reactions realized in the period 2000 to 2020. 1 Introduction 2 Nickel Catalysis 3 Palladium Catalysis 4 Iron Catalysis 5 Catalysis by Other Transition Metals 5.1 Cobalt Catalysis 5.2 Copper Catalysis 5.3 Manganese Catalysis 5.4 Chromium Catalysis 6 Conclusion [ABSTRACT FROM AUTHOR]

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A series of 2,4,5-trisubstituted-imidazoles has been synthesized with good to excellent yields by the one-pot condensation reaction of 1,2-dicarbonyl compounds, benzaldehydes, and ammonium acetate in the presence of 4 Å molecular sieves modified with titanium(IV) as an efficient heterogeneous catalyst. The catalyst could be recovered easily and reused without significant loss of activity. [ABSTRACT FROM AUTHOR]