5-Acetoxy-5-phenyl-2 acetate

A few acetates of phenols have been used extensively as probes to investigate esterases, e.g., phenyl acetate (7.15), 4-nitrophenyl acetate (7.16), a-naphthyl acetate (7.17) and 7-acetoxy-4-mc(hyl-27/-[l bcnzopyran-2-onc (4-methylumbelliferyl acetate, 7.18). Such substrates are easy to handle and their phenolic metabolite is readily analyzed, allowing convenient monitoring of the reaction. 

A more recent study [265] is concerned with the action of a large number of nucleophiles of different types on the hydrolyses of phenyl acetate, p-nitrophenyl acetate, 2,4-dinitrophenyl acetate, and 1-acetoxy-4-methoxypyridinium ion. 

The chloro[exo-5-acetoxytricyclo[2.2.1.0 ]hept-enifo-3-yl]dipyridinepalladium complex 17 [prepared from norbornadiene and palladium(II) chloride bisbenzonitrile complex with subsequent substitution and ligand exchange ] underwent exchange with acetoxy(phenyl)mer-cury, analogous to the known exchange reactions between palladium(II) chloride or acetate and phenylmercury salts, to afford a mixture of products, including biphenyl (54%), exo,exo-3,5-diacetoxytricyclo[2.2.1.0 ]heptane (19,20%) and chloro[exo-5-acetoxytricyclo[2.2.1.0 ]-hept-e Jo-3-yl]mercury (18, 57%). 

The destruction of heterocycles condensed to the 1,2,4-triazine ring can also be treated as a method of substituent modification. For example, the formation of 3-[acetoxy(phenyl)-methyl]-l,2,4-triazines 24 by treatment of [l,2,3]triazolo[5,l-c][l,2,4]triazines with acetic acid,340 and the degradation of the pyrimido[5,4-c]-1.2,4-triazines353 and pyrimido[4,5-e]-1,2,4-triazines to afford 25 and 26, respectively.331 354 Further reactions of this type are discussed in a previous review.8 For a synthesis of l,2,4-triazine-3,5,6-tricarboxylic acid from pyrrolo[2,l-c]benzo-l,2,4-triazine, see also Houben-Weyl, Vol. 4/1 b, p 643. 

Several selective cleavage reactions (classed as miscellaneous reactions in the introduction to this section) have been described. Thus, preferential 0-deacetylation of a phenyl acetate in the presence of an alkyl acetate occurred when 3-(4-acetoxy-3-methoxyphenyl)propylacetate was allowed to stand in pyrrolidine (or pyrrolidine in dichloromethane) at ambient temperature for 3 mins, followed by acidic quenching, to give 3-(3-methoxy-4-hydroxy)propylacetate in more than 80% yield (ref. 88). 

CgHjiBrxO Fomiddehyd-big.[3.6-dibroin-4.acetoxy-2.5-diniethyl.phenyl]-acetal 6,916. 

Furthermore, the catalytic allylation of malonate with optically active (S)-( )-3-acetoxy-l-phenyl-1-butene (4) yields the (S)-( )-malonates 7 and 8 in a ratio of 92 8. Thus overall retention is observed in the catalytic reaction[23]. The intermediate complex 6 is formed by inversion. Then in the catalytic reaction of (5 )-(Z)-3-acetoxy-l-phenyl-l-butene (9) with malonate, the oxidative addition generates the complex 10, which has the sterically disfavored anti form. Then the n-a ir rearrangement (rotation) of the complex 10 moves the Pd from front to the rear side to give the favored syn complex 6, which has the same configuration as that from the (5 )-( )-acetate 4. Finally the (S)-( )-mal-onates 7 and 8 are obtained in a ratio of 90 10. Thus the reaction of (Z)-acetate 9 proceeds by inversion, n-a-ir rearrangement and inversion of configuration accompanied by Z to isomerization[24]. 

A) Suspend lOg of 7-chloro-l -dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide in 150 ml of acetic anhydride and warm on a steam bath with stirring until all the solid has dissolved. Cool and filter off crystalline, analytically pure 3-acetoxy-7-chloro-1,3-dihydro-5-phenyl-2H-1 /t-benzodiazepin-2-one, melting point 242°C to 243°C. 

According to British Patent 1,022,645 3.4 g of 3-acetoxy-7-chloro-1-methyl-5-phenyl-1,3-dihy-dro-2H-1,4-benzodiazepin-2-one suspended in 80 ml alcohol was treated with 6 ml of 4 N NaOH. After Complete solution had taken place, a solid precipitated this solid was redissolyed by the addition of 80 ml of water. The solution was acidified with acetic acid to give white crystals which were recrystallized from alcohol to yield 7-chloro-3-hydroxy-5-phenyl-1-methvl-1,3-dihydro-2H-1,4-benzodiazepin-2-one, MP 119° to 121°C. 

Cleavage of the acetate unit(s) in 5-acetoxy- and 3,5-diacetoxy-4-phenyl-l-benzothiepins 11 with potassium carbonate in methanol at room temperature does not stop at the diketone stage, but further undergoes ring contraction to the thiophene derivative 12 in 55-80% yield.90... 

Phenylthio acetals are much more easily prepared from the corresponding 4-acetoxy-l,3-dioxanes [45] (Eq. 29). The dioxane 125 gave the phenyl sulfides 185 in essentially quantitative yield on treatment with BF3 OEt2 and thiophenol at -78 °C. This method has been used to prepare compound 185 on a 40 g scale. 

For unsymmetrical allylic systems both the regiochemistry and stereochemistry of the substitution are critical issues. The palladium normally bonds anti to the acetate leaving group. The same products are obtained from 2-acetoxy-4-phenyl-3-butene and 1 -acetoxy-l-phenyl-2-butene, indicating a common intermediate. The same product mixture is also obtained from the Z-reactants, indicating rapid ,Z-equilibration in the allylpalladium intermediate.118... 

Essentially the same substituents as listed above may be present in the alkene being substituted, with the possible exception of chloro, alkoxy and acetoxy groups on vinyl or allyl carbons. These groups, especially chloro, may be lost or partially lost with palladium when the final elimination step occurs. For example, vinyl acetate, iodobenzene and triethylamine with a palladium acetate-triphenylphosphine catalyst at 100 C form mainly (E)-stilbene, presumably via phenylation of styrene formed in the first arylation step (equation 21 ).6 ... 

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