Aromatic aldehydes. Mesitaldehyde

The preparation of mesitaldehyde is an example of a generally applicable method for the preparation of aromatic aldehydes by treatment of aromatic compounds with dichloromethyl methyl... 

A general synthesis of c-fused pyridines under neutral conditions involves the thermolysis of vinyl azides, prepared from aromatic aldehydes that bear an ortho methyl group and ethyl azidoacetate. Thus thermolysis of the vinyl azide (151) from mesitaldehyde (150) gives the isoquinoline (152) in 45—50% yield (Scheme... 

Figure 10.2 illustrates selected examples of these epoxide products. Aromatic and heteroaromatic aldehydes proved to be excellent substrates, regardless of steric or electronic effects, with the exception of pyridine carboxaldehydes. Yields of aliphatic and a,/ -unsaturated aldehydes were more varied, though the enantio-selectivities were always excellent. The scope of tosylhydrazone salts that could be reacted with benzaldehyde was also tested (Fig. 10.3) [29]. Electron-rich aromatic tosylhydrazones gave epoxides in excellent selectivity and good yield, except for the mesitaldehyde-derived hydrazone. Heteroaromatic, electron-poor aromatic and a,/ -unsaturated-derived hydrazones gave more varied results, and some substrates were not compatible with the catalytic conditions described. The use of stoichiometric amounts of preformed sulfonium salt derived from 4 has been shown to be suitable for a wider range of substrates, including those that are incompatible with the catalytic cycle, and the sulfide can be recovered quantitatively afterwards [31]. Overall, the demonstrated scope of this in situ protocol is wider than that of the alkylation/deprotonation protocol, and the extensive substrate...

---