Synthetic Applications of the Carbonyl Generating Grob Fragmentation

Synthetic applications of carbonyl generating Grob fragmentation are presented. Grob-type fragmentation of quaternary γ-amino alcohols gives access to unsaturated aldehydes and ketones with a (Z)-double bond. In an anodic Grob fragmentation, 3-substituted 6-hydroxy-2-norbornanecarboxylic acids stereospecifically gives 3,4-disubstituted cyclopentenes. In the total synthesis of nonracemic coraxeniolide A, a very similar structural motive is generated by Grob fragmentation. In the synthesis of periplanone-B, the tricyclic system is generated by IMDA reaction between a furan and an allene moiety and a 10-membered ring is introduced by Grob fragmentation. When the fragmentation was performed in methanol to obtain the methoxy acetal directly, oxonium ion is generated and trapped with methanol to form MOM ether.