Retroaldol reaction, ring opening

Retroaldol reaction, ring opening by - 26, 227 Retro-benzilic acid-type rearrangement imidazoles by - 28, 959 Retrodiene scission... 

Photochemical cyclobutane annealings are much more promising and find their way into synthesis to a greater extent. Photochemical cycloaddition reactions to enolized 1,3-diketones and consecutive ring openings via retroaldol reactions have been applied in ring expansion reactions numerous times. 

Phenyl-substituted oxiranes may be reduced in DMF akin to benzyl ethers by direct and indirect methods the regioselectivity is slightly higher in the indirect reduction [76]. Benzoyloxiranes can be reduced in MeCN to aldoles addition of acetic acid prevents a retroaldol reaction catalyzed by the EGB [77]. The ring opening is analogous to the reduction of 2-alkoxyacetophenone to acetophenone. 

The C-acyl compounds 320 underwent hydration on being heated in aqueous alcohol, but the resulting unstable azacyclols 321 underwent retroaldol fission and afforded the ring-opened derivatives 322. ° When the reaction was carried out in deuterium oxide or in labeled water, the incorporation of deuterium in the position a to the RCO group or of 0 into the ureido carbonyl group was observed. ... 

N Heterocyclic oxo compounds by base-catalyzed retroaldol reaction 2-Pyridone ring opening... 

During the synthesis of the Woodward reserpine precursor (17 Scheme 4), Peailman used the protected acylacetal (13) to control the stereochemistry of an intramolecular photochemical cycloaddition to (14). The strategy for opening the cyclobutane ring employed the Baeyer-Villiger reaction to convert the 7-keto ester (15) to a 3-hydroxy ester (16), which underwent retroaldolization to (17). 

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