Aldehyde group, introduction with formyl

The acetylacetonates of chromium, cobalt, and rhodium were found to react with dimethylformamide in the presence of phosphorus oxychloride to yield formyl-substituted chelates (10). This is a well known technique for the introduction of an aldehyde group into reactive aromatic systems. The formylation of the chelate rings is a slow reaction, and by controlling the conditions it is possible to... 

The well-known powerful basic catalyst 4-dimethylaminopyridine has been the inspiration for a new transesterification catalyst for a-hydroxy esters (5). The designer compound is 2-formyl-4-pyrrolidinopyridine (6). By the introduction of an aldehyde group into the pyridine ring at the 2-position, the ready formation from (5) of a hemi-acetal (7) makes possible, via a covalent pre-association step, a facile displacement by pyridine nitrogen of the aryloxy group of the a-hydroxy ester (5). The product of this process, a tricyclic pyridinium compound (9), is formed by a nucleophilic mechanism (Scheme 1, pathway b), and interaction with methanol then leads to the methyl ester of the a-hydroxy acid (10) and regeneration of the catalyst. However, a study of the mechanism of this catalytic process discounted the nucleophilic mechanism and provided clear evidence instead for a general base mechanism, which proceeds via a dioxolanone (8) (Scheme 1, pathway a) ... 

It was discovered by Roelen in 1938 and is the oldest and largest volume catalytic reaction of alkenes, with the conversion of propylene to butyraldehyde being the mosi important. About 5 million tons of aldehydes and aldehyde derivatives (mostly alcohols) are produced annually making the process the most important industrial synthesis using a metal carbonyl complex as a catalyst. The name hydroformylation arises from the fact that in a formal sense a hydrogen atom and. formyl group are added across a double bond. The net result of the process is extension of (he carbon chain by one and introduction of oxygen into the molecule. 

Introduction of the more bulky carbohydrate moiety increases the shielding on one of the faces of the formyl group. The D-galactose derived aldehyde 10 adds to 1-methoxy-l.3-butadiene (1) with complete diastereoselectivity. D-Ribose and D-glucose derived aldehydes 13 and 14 are less efficient, but the cycloadducts 15 and 17 are still produced with high diastereomeric ratios22. 

---