Various imidazolylsilane derivatives were synthesized by a trans-silylation procedure between 1-(trimethylsilyl)imidazoles and chlorosilanes. Among them, tris- and tetrakis(imidazol-1-yl)silane compounds reacted smoothly with free carboxylic acids to form the corresponding 1-acylimidazoles, which subsequently underwent condensation with amines to afford carboxamides in good to high yields. These results indicate that novel reagents containing silicon–imidazole linkage are effectively utilized as dehydrating reagents to form carboxylic acid derivatives from free carboxylic acids and nucleophiles under mild conditions.

In order to examine the effect of cemented tungsten carbide dust on the animal lung, saline suspensions were intratracheally administered into the lungs of rats in a single dosage. About one‐fifth of the animals died during the first three days. The acute response of the lungs was hemorrhagic edema with intense alveolar congestion. The animals killed at six months all presented pulmonary lesions of patchy fibrosis in the vicinity of the deposited dusts, occasionally associated with focal traction emphysema and broncho‐bronchiolar ectasia. At twelve months, two‐third of the animals had neither fibrosis nor dust deposition, although the remaining animals showed pulmonary lesions similar to those seen in the six‐months responders. Pibrosis of the lungs seemed to consist of collapsed alveoli with condensation of the preexistent reticulin fibers, but without noticeable collagenization. It is supposed that both the early toxic and the late flbrogenic effects of the carbide dust are attributable to the cytotoxic action of cobalt present in the dust particles. It is possible that recovery of the pulmonary lesions results from removal of the dusts from the lesions.

Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine-derived catalyst that bears both a sterically hindered N1-9-anthracenylmethyl group and a strongly electron withdrawing 9-O-3,5-bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and alpha,beta-unsaturated ketones followed by lactonization. Optically active 3,4-dihydropyran-2-one derivatives were obtained in high yields with excellent control of enantio- and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month.

The use of tetraalkoxysilanes, particularly tetrakis(perfluoroalkoxy)silanes, in dehydration condensation of carboxylic acids with amines was investigated. Tetrakis(1,1,1,3,3,3-hexafluoro-2-propoxy)silane, Si[OCH(CF3)2]4, prepared easily from silicon tetrachloride and sodium 1,1,1,3,3,3-hexafluoro-2-propoxide, was found to be an effective dehydrating reagent for preparing various carboxamides in good to high yields from the corresponding carboxylic acids and amines.