No pressure: A simple monomeric tungstate, [WO4]2−, serves as a highly efficient homogeneous catalyst for various transformations of CO2 at atmospheric pressure. The tungsten‐oxo moiety activates CO2 and the substrate simultaneously. The catalyst system is high yielding and applicable to a wide range of substrates such as amines (see scheme), 2‐aminobenzonitriles, and propargylic alcohols.

A simple monomeric tungstate, TBA(2)[WO(4)] (I, TBA = tetra-n-butylammonium), could act as an efficient homogeneous catalyst for chemical fixation of CO(2) with 2-aminobenzonitriles to quinazoline-2,4(1H,3H)-diones. Various kinds of structurally diverse 2-aminobenzonitriles could be converted into the corresponding quinazoline-2,4(1H,3H)-diones in high yields at atmospheric pressure of CO(2). Reactions of inactive 2-amino-4-chlorobenzonitrile and 2-amino-5-nitrobenzonitrile at 2 MPa of CO(2) also selectively proceeded. The present system was applicable to a g-scale reaction of 2-amino-5-fluorobenzonitrile (10 mmol scale) with CO(2) and 1.69 g of analytically pure quinazoline-2,4(1H,3H)-dione could be isolated. In this case, the turnover number reached up to 938 and the value was the highest among those reported for base-mediated systems so far. NMR spectroscopies showed formation of the corresponding carbamic acid through the simultaneous activation of both 2-aminobenzonitirile and CO(2) by I. Kinetic and computational studies revealed that I plays an important role in conversion of the carbamic acid into the product.

A tetra-n-butylammonium (TBA) salt of a γ-Keggin -6-charged germanodecatungstate, [γ-H(2)GeW(10)O(36)](6-) (I), could act as an efficient homogeneous catalyst for Knoevenagel condensation of active methylene compounds with carbonyl compounds.

Ohne Druck: Ein einfaches monomeres Wolframat, [WO4]2−, dient als homogener Katalysator für verschiedene Umsetzungen von CO2 bei Atmosphärendruck. Die Wolfram‐Oxo‐Gruppierung aktiviert gleichzeitig CO2 und das Substrat. Das Katalysatorsystem liefert hohe Ausbeuten und kann auf eine Bandbreite von Substraten wie Amine (siehe Schema), 2‐Aminobenzonitrile und Propargylalkohole angewendet werden.

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