Benzoate Esters Bz

The situation is more complicated in the case of 5-bromohexopyranose derivatives, because products of both endo- and exo-elimination may be formed, and available evidence indicates that, with 5-bromo-/ -D-glucopyr-anose esters, base-catalyzed elimination favors the production of endo-alkenes following loss of axial hydrogen and bromine atoms. Alternatively, treatment with zinc-acetic acid gives, mainly, the products of exo-elimination.90 From the acetate 164 (R = Ac) and the benzoate 164 (R = Bz), the 4-enes (165, R = Ac, Bz) were both obtained in 65% yield following treatment with 1,5-diazabicyclo[5.4.0]undec-5-ene, whereas zinc - acetic acid afforded the 5-enes (166, R = Ac, Bz) in 59 and 67% yield. The isomeric endo products 167 (R = Ac, Bz) were isolated in 15 and 11% yield, and, from the... 

Figure 8-7. Correlation between equilibrium constant for esterification and solubility of water in the solvent. Equilibrium constant was defined as [Ester]/([Alcohol].[Acid]), for reactions at fixed water activity (close to 1). Solvents are bb, butyl benzoate be, bromoethane bk, dibutyl ketone bp, dibutyl phthalate bz, benzene ca, 1,1,1-trichloroethane cf, chloroform ct, carbon tetrachloride cy, trichloroethylene ee, ethyl ether ek, diethyl ketone ep, diethyl phthalate hd, hexadecane hx, hexane me, methylene chloride mk, methyl iso-butyl ketone nm, nitromethane oc, /so-octane pe, iso-propyl ether tl, toluene. Valivety et al...

Esters (ROCOR ) can be easily prepared by reacting an alcohol (ROH) with an acid chloride (R COCl) and base. Deprotection is generally accomplished by basic hydrolysis or alcoholysis of the ester. Commonly used ester groups include acetate (-COCH3, or Ac) and benzoate (-COPh, or Bz).The pivaloate ester (-COr-Bu, or Pv) is useful for selective acylation of a primary alcohol in the presence of more hindered secondary or tertiary alcohols. 

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