Oximino derivatives, cycloaddition

Cycloaddition of oximino derivatives 261 with dienes 262 afforded the adduct 263, which was converted to pyridines 264 by either heating in EtOH or base-promoted elimination. ... 

The cycloaddition does provide a useful route to certain pyridine derivatives. - For example, oxygenated dienes (67) add to oximino dienophile (68) to afford adducts (69) in a totally regioselective manner (equation 22). Treatment of this adduct with base provides the pyridine amide (70). 

Imidazole-4-carboxylates have been made from amidines derived from or-ainino acids (see Section 2.2.1 and Table 2.2.1), by Claisen rearrangement of the adduct formed when an arylamidoxime reacts with a propiolate ester (see Section 2.2.1 and Scheme 2.2.6), from a-aminocarbonyls with cyanates or thiocyanates (see Section 4.1 and Table 4.1.1), from a-oximino- 6-dicarbonyl compounds heated with an aUcylamine (see Section 4.1 and Scheme 4.1.7), and by anionic cycloaddition of an alkyl isocyanoacetate to diethoxyacetonitrile (see Section 4.2 and Scheme 4.2.11 see also Scheme 4.2.12). A further useful approach is to use an appropriate tricarbonyl compound with an aldehyde and a source of ammonia (see Chapter and Scheme 5.1.1). Irradiation of 1-alkenyltetrazoles bearing an ester substituent may have applications (see Section 6.1.2.3). 

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See also in sourсe #XX -- [ ]

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