Showing papers in "Journal of the American Chemical Society in 1974"

New cross-aldol reactions. Reactions of silyl enol ethers with carbonyl compounds activated by titanium tetrachloride

Abstract: Synopsis: With the addition of titanium tetrachloride, silyl enol ethers can react with either aldehydes or ketones forming crossed aldol products. The carbonyl group of the aldehyde or ketone is activated by titanium tetrachloride, allowing for nucleophilic attack by a silyl enol ether at the carbonyl carbon (a titanium chelate forms as an intermediate). This addition reaction is dependent upon the metal salt, solvent, and temperature used. Critique: The fact that various reaction conditions were studied to find optimal reaction conditions that gave the highest yield of cross-aldol addition products strengthened the findings in this paper. Mukaiyama and coworkers concluded first that titanium chloride was best for this reaction compared to boron trifluoride etherate and stannic chloride. Secondly, it was observed that methylene chloride gave cross-aldol products in good yield while no reaction was observed in both diethyl ether and THF. Finally, reaction with aldehydes is favored at -78 o C while ketone reaction is favored at room temperature. It was also interesting to see that the use of unsymmetric ketones allows for regiospecific addition reactions at the olefinic position on the silyl enol ether.

Palladium-catalyzed formylation of aryl, heterocyclic, and vinylic halides

Abstract: Die Bromide (I) werden in Gegenwart von Tri-n-butyl- oder Triathylamin und dem Pd-Komplex (II) mit einem CO-H2-Gemisch bei 80 bis 150°C uber die sich wahrscheinlich zunachst bildenden Organo-Pd-Verbindungen zu den Aldehyden (III) formyliert.