Catalysis monoacetate

An enantio-selective enzymatic hydrolysis of meso( )-2,5-diacetoxy-3-hexene gives (+)-( )-(25 ,5/ )-5-acetoxy-3-hexen-2-ol in 77% yield (92% ee).97 The monoacetate with its two allylic groups offers possibilities for stereo-controlled introduction of nucleophiles via Pd(0) catalysis. Synthesis of both enantiomers of the Carpenter bee pheromone based on this strategy is presented in Scheme 5.14.98... 

Higuchi et al. (1971) reported an example of possible bifunctional catalysis in the hydrolysis of the monosuccinate ester of hexa-chlorophene [7]. The monoacetate ester hydrolyses 500 times faster than the diacetate below pH 8, and the monosuccinate hydrolyses... 

Examples of possible intramolecular general acid-base catalysis were reported by Kupchan et al. (1962). The methanolysis of coprostanol acetate and coprostane 3/3, 5/3-diol 3-monoacetate [12] in aqueous methanol was conducted in triethylamine-triethyl-ammonium acetate buffer. The rates of methanolysis at constant... 

Cacciapaglia, R., Casnati, A.. Mandolini, L. and Ungaro, R. (1992) Remarkable metal ion catalysis of methanolysis of p-tert-butylcalix[4]ai ene-crown-5 monoacetate. Chem. Commun., 1291. 

In another interesting example of pseudo intramolecular catalysis, the halftime for the methanolysis of the calixarene monoacetate 290a with Mc4N OMe in MeOH at 25 °C is reduced from 34 weeks to 8 seconds by the addition of The reactive species is thought to be the Ba complex of the... 

The selective protection of one carbonyl group in a -dicarbonyl system often presents special problems. Such a system, at any rate its more or less predominant enolic tautomer, can be regarded as a vmylogous carboxylic acid a monoenol ether as a vinylogous ester, and a monoacetal or -ketal as an analogue of an ortho-ester. Equilibrium between the two latter can be established both by acid and by base catalysis [226]. 

Similar behaviour is found with catechol monoacetate [21] and catechol monocinnamoate [22]. With catechol monosuccinate intramolecular general base catalysis by the phenolate group takes over from intramolecular nucleophilic catalysis by the carboxylate group... 

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