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.

No abstract

In the presence of a simple combined catalyst of a tungstate monomer (TBA2WO4, TBA: tetra-n-butylammonium) and rhodium acetate (Rh2(OAc)4), hydrosilylation of various types of substances including ketone, aldehyde, carbon dioxide, alkene, nitrile, and furan derivatives efficiently proceeded, affording the corresponding hydrosilylation products in moderate to high yields (≥63% yields). In addition, the present system was also applicable to the one-pot reduction of benzamide to benzylamine (95% yield).

Catalytic N‐alkylation of indoles is challenging because the N1 nitrogen atoms are inert toward electrophilic reagents. Herein, an organic‐solvent‐soluble alkylammonium salt of a simple monomeric phosphate ion, [PO4]3−, with a high charge density acts as an efficient homogeneous catalyst for selective N‐alkylation of indoles with α,β‐unsaturated compounds. For the reaction of indole with ethyl acrylate, the turnover number reached up to 36 and the turnover frequency was 216 h−1; these values are the highest among those reported for base‐mediated systems so far. In the presence of [PO4]3− ions, various combinations of nitrogen nucleophiles (ten examples) and α,β‐unsaturated compounds (four examples) were efficiently converted to the desired N‐alkylated products in high yields. NMR and IR spectroscopies showed formation of the indolyl anion through the activation of indole by the [PO4]3− ion, which plays an important role in the present N‐alkylation.

A palladium‐catalyzed annulation reaction of alkynylborates with o‐iodophenyl ketones to form indenes is described. Highly substituted indene skeletons are efficiently constructed with site‐specific installation of the substituents.