Anionic rearrangement unsaturated carboxylic acids

The benzotriazolyl derivative of acrolein acetal, compound 882, is lithiated, treated with chlorodiphenylphosphine, and the obtained intermediate is oxidized with hydrogen peroxide to phosphine oxide 883 (Scheme 145). The relatively acidic proton in derivative 883 is easily removed by a base, and the obtained anion adds to a carbonyl group of aldehyde or ketone. Subsequent rearrangement and elimination of the phosphorane group generates diene 884. For the derivatives of aldehydes (884, R2 = H), (E)-(E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of P,y-unsaturated carboxylic acids 885 < 1997JOC4131>. 

The above discourse of the Perkin Reaction is self-explanatory in which benzaldehyde and acetic anhydride interacts to form an anion (I) that undergoes molecular rearrangement to give another anion (II). The resulting restructured anion (II) reacts with acetic anhydride to form an intermediate which subsequently undergoes hydrolysis in the presence of a base to give rise to the formation of an a, P-unsaturated carboxylic acid i.e., cinnamic acid. 

A new four-carbon annulation procedure is shown in Scheme 14, whereby the dienolate anion of an unsaturated carboxylic acid (99) is added to a ketone to give an acid which upon rearrangement at... 

Wittig and anionic oxy-Cope rearrangements using potassium hydride. The anionic oxy-Cope rearrangement went through a chair-like transition state to yield the iyn-substituted aldehydes 257, which were oxidized to acid 258. Treatment of 8,e-unsaturated carboxylic acids 258 with either iodine or phenylselenium chloride afforded the cyclized iodo-/phenylselenolactones 259-261 as a mixture of diaste-reomers. In most cases, lactone 259 was obtained as the major or sole product. 

---