Pivaloate

Guanidine, EtOH, CH2CI2, rt, 85-100% yield.Acetamides, benzoates, and pivaloates are stable under these conditions. Phenolic acetates can be removed in the presence of primary and secondary acetates with excellent selectivity. 

Aqueous MeNH2, 20°, /,/2 = 3 h. In this case the 5 -position of uridine was deprotected. Acetates can be cleaved selectively in the presence of a pivaloate with NH3/MeOH. 

Fungus, Currulania lunata, 6 h, 64% yield." In this case a 21-pivaloate was removed from a steroid. 

AC2O or AcCl, Pyr, DMAP, 24-80°, 1-40 h, 72-95% yield. The use of DMAP increases the rate of acylation by a factor of lO. These conditions acylate most alcohols, including tertiary alcohols. The use of DMAP (4-A,A-dimethylaminopyridine) as a catalyst to improve the rate of esterification is quite general and works for other esters as well, but it is not effective with hindered anhydrides such as pivaloic anhydride. The phosphine i (48-99% yield) and Bu3P have been developed as active acylation catalysts for acetates and benzoates. 

Mg, MeOH or Mg(OMe)2 iri MeOH. The acetate is cleaved in the presence of the benzoate and pivaloate (76-96% yield). The relative rates of cleavage are as follows p-nitrobenzoate > acetate > benzoate > pivaloate acetamide. Tertiary acetates are not cleaved. ... 

BU2AIH, CH2CI2, -78°, 95% yield. /-BU2AIH, CH2CI2, toluene, 84% yield. Three pivaloates were cleaved from a zaragozic acid intermediate. The use of THE or ether as solvent failed to remove all three. 

EtMgBr, Et20, it, 1 h, 90-100% yield. These conditions were used to prevent a neighboring silyl ether from migrating. Ethylmagnesium chloride is much more reactive thus, the reaction can be run at —42°, giving a 90% yield of the alcohol. Acetates and pivaloates are also cleaved. 

Formate, 276 Acetate, 276 Levulinate, 278 Pivaloate, 278 Benzoate, 279 9-Fluorenecarboxylate, 280 Xanthenecarboxylate, 280... 

Pyrrolizinone 246 is a key intermediate in the synthesis of the ML-3000 drug which was described by Cossy and Belotti <1997JOC7900> this pyrrolizinone intermediate was constructed in one-step (68%), via a thermal acid-promoted intramolecular bicyclization of the iu-acetylenic amino ester 245 by heating at 150 °C in presence of pivaloic acid (1 equiv) (Scheme 66). 

The preparation of the requisite y-keto-p-toluenesulfonate rac-35 as homo-Favorskii precursor commenced with commercially available 2,5-dihy-droanisole (36) that was protected and epoxidized to acetal rac-31 (Scheme 11). Regioselective opening of the epoxide with p-chlorophenylse-lenide followed by sequential oxidation to the selenoxide and thermal elimination generated an allylic alcohol that was protected to give pivaloate rac-38. 

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