Intermolecular dialdehydes

The 1,5- and 1,6-dialdehydes 22 and 24 undergo the annulative pinacol coupling to give the cyclic vzc-diols 23 and 25, respectively (Scheme 13) [29]. The vanadium-catalyzed intramolecular coupling reaction of 1,5-diketone 26 also proceeds with excellent selectivity (Scheme 14) although the intermolecular coupling of ketones such as acetophenone results in low diastereoselectivity under these conditions [21]. 

Simultaneous decrease in the content of diene conjugates and increase in the content of Schiff bases evidence the quick shift of pro-/antioxidant equilibrium, generation of reactive radicals, and damage of cell membranes in EAC cells, because Schiff bases, generated as a consequence of interaction of malonic dialdehyde with aminogroups of phospholipids and proteins, are highly reactive compounds causing polycondensation of molecules and formation of intermolecular bonds. 

The preparation of lactones via intramolecular catalytic esterification can be carried out by the Tishchenko reaction of dialdehydes. Alkaline earth metal oxides have been shown to be active not only for the intermolecular Tishchenko reaction, but also for the intramolecular Tishchenko lactonization. Thus, these solid catalysts have been applied for the Tishchenko reaction of o-phthalaldehyde to phthalide 182) (Scheme 34). 

In analogy to intermolecular pinacolic coupling reactions, organometallic dialdehydes have served as precursors for the intramolecular version of the reaction, affording cyclic 1,2-diols [39]. Both arene chromium tricarbonyl (Eq. 29) and ferrocene complexes (Eq. 30) afford excellent yields of the desired products. 

Discovered more than a century ago, the Paal-Knorr pyrrole synthesis is similar to the Knorr synthesis. It is the intermolecular condensation of a primary amine (or ammonia) with a 1,4-diketone (or 1,4-dialdehyde) to give pyrroles. ... 

It is sometimes said that cross-linking takes place during formalization. However, as has already been mentioned in the discussion on acetalization in Section 4.3.4, intermolecular acetalization leading to cross-linking occurs only to a very small extent, if any. When cross-linking is needed, it is advisable to use a dialdehyde, such as terephthalaldehyde [119], and acetalyl sulfide [120], which enables us to obtain sufficiently heat-resistant PVA fiber without heat treatment, although the fiber is brittle compared to fibers that are acetalized with monoaldehydes. 

Intermolecular coupling of dialdehydes and diketones constitutes a newly developed route to polymers [71]. 

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