Secondary products formation prominent reactions

Although acetone was a major product, it was not observed by infrared spectroscopy. Flowing helium/acetone over the catalyst at room temperature gave a prominent carbonyl band at 1723 cm 1 (not show here). In this study, a DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) cell was placed in front of a fixed reactor DRIFTS only monitored the adsorbed and gaseous species in the front end of the catalyst bed. The absence of acetone s carbonyl IR band in Figure 3 and its presence in the reactor effluent suggest the following possibilities (i) acetone formation from partial oxidation is slower than epoxidation to form PO and/or (ii) acetone is produced from a secondary reaction of PO. 

Phenethylisoquinoline alkaloids constitute another important group of tyrosine-derived secondary metabolites. This class of natural products with colchicine (54) as most prominent member is obtained when aldehyde 43 is employed in a condensation reaction with dopamine, followed by a Pictet-Spengler cyclization reaction. The difference to benzyltetrahydroisoquinoline alkaloids is an additional carbon between the tetrahydroisoquinoline core and the aromatic ring. As outlined in Scheme 12.9, aldehyde 43 is derived from phenylalanine (42) via intermediary formation of 4-hydroxycinnamaldehyde. The formation of the tetrahydroisoquinoline system 44 from dopamine (4) and 4-hydroxydihydrocinnamaldehyde (43) is followed... 

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