Alcoholysis mandelic acid

Toniolo reported the carbonylation of aromatic aldehydes containing electron-donating substituents with a Pd/PPh3 catalyst system in the presence of HC1 to give phenylacetic acid derivatives [64]. No activity was observed in the absence of PPI13 or HC1, and high yields could be achieved with alkanols as solvent (e.g., EtOH). It is believed that the mechanism involves HC1 addition to the aldehyde, with the resultant chlorohydrin being subject to oxidative addition to Pd, CO insertion, and alcoholysis. Upon Cl -o- OR substitution with the formed mandelic acid derivative, a second carbonylation takes place,... 

Scheme 6.27 Typical P-alkoxy alcohols obtained from the highly regioselective alcoholysis of styrene oxides catalyzed by thiourea 9 and mandelic acid 20 in a cooperative organocatalytic system.

Under optimized conditions regarding the choice of Br0nsted acid (mandelic acid 20), stoichiometry (1 1 ratio 9 and mandelic acid 20), solvent (the respective alcohol neat conditions), temperature (rt or 50°C), and catalyst loading (lmol% 9 and lmol% mandelic acid 20) electron-rich and electron-deficient styrene oxides underwent alcoholysis with simple aliphatic, stericaUy demanding as well as unsaturated and acid-labile alcohols. The completely regioselective (>99%) alcoholysis was reported to produce the corresponding P-aUcoxy alcohols 1-10 in moderate (41%) to good (89%) yields without noticeable decomposition or polymerization reactions of acid-labile substrates (Scheme 6.27). Notably, aU uncatalyzed reference experiments showed no conversion even after two weeks under otherwise identical conditions. 

Scheme 6.28 Mechanistic proposal for the regioselective alcoholysis of styrene oxides utilizing a cooperative Bronsted acid-type organocatalytic system comprised of thiourea 9 and mandelic acid 20.

Alcoholysis. Styrene oxides open on treatment with ROH in the presence of mandelic acid and A(,iV -di[3,5-bis(trifluotDmethyl)phenyl]thiourea in a regioselective manner, due to cooperative interaction of the Bronsted acids. ... 

---