Claison rearrangement

Potassium Amides. The strong, extremely soluble, stable, and nonnucleophilic potassium amide base (42), potassium hexamethyldisilazane [40949-94-8] (KHMDS), KN [Si(CH2]2, pX = 28, has been developed and commercialized. KHMDS, ideal for regio/stereospecific deprotonation and enolization reactions for less acidic compounds, is available in both THF and toluene solutions. It has demonstrated benefits for reactions involving kinetic enolates (43), alkylation and acylation (44), Wittig reaction (45), epoxidation (46), Ireland-Claison rearrangement (47,48), isomerization (49,50), Darzen reaction (51), Dieckmann condensation (52), cyclization (53), chain and ring expansion (54,55), and elimination (56). 

Reaction of the quinone (12) with vinyl aziridine affords the dihydroazepinoquinone (14) in good yield <95TL4787>. The reaction proceeds via an aza-Claison rearrangement of the intermediate (13) followed by a sigmatropic rearrangement (Scheme 2). 

Sigmatropic reactions. In these, an allylic a bond at one end of a tt system appears to migrate to the other end of the tt system. The tt bonds change position, but the total number of a and tt bonds is the same, as in the Cope and Claison rearrangements. 

Claison rearrangement of the vinyl ketene aminal (175) offers a new route to 7-substituted caprolactams (176) <92TL6857>. 

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