Wax esters were synthesized in a solvent free system catalyzed by immobilized lipase from Candida sp. 99-125, with oleic acid and cetyl alcohol. The effects of substrate molar ratio, lipase dosage and water removal were investigated in a 50 ml flask incubated in a thermostatic cultivation cabinet. The optimized conditions were: temperature 40 ℃, shaking at 170 r·min-1, acid/alcohol molar ratio 1:0.9, lipase dosage in 10% (by mass) of oleic acid, and open reaction for water removal. As a result, the conversion rate reached 98% for reaction of 8 h. The volume of reactor was scaled up to 1 L three-neck flask. The optimized parameters were: 200 r·min-1 agitation speed, 2.5% (by mass) lipase dosage, others were the same as the parameters described above. The conversion rate reached 95% for reaction of 24 h. The lipase retained 46% conversion rate after reuse for 6, 7 batches. The products were purified by removing remained cetyl alcohol and fatty acids with ethanol and saturated sodium carbonate so-lution, respectively. The purity of the wax ester, cetyl oleate, was 96%. The physical and chemical properties of cetyl oleate were tested and compared with those of jojoba oil. The results show that the product cetyl oleate has great potential to use as the substitute of natural jojoba oil. 相似文献
A ruthenium-catalyzed C(sp2)−H acyloxylation of 2-aroyl pyridine derivatives with simple sodium carboxylate utilizing transformable directing groups is described. This protocol features broad functional group tolerance and chemo- and regio-selectivity, providing the acyloxylation products in 45%-84%yield. Furthermore, the synthetic utility of this protocol was demonstrated by the late-stage functionalization of pharmaceutical compounds. Notably, the acyloxylation products could be further transformed into a variety of useful heterocycles under mild conditions. 相似文献
An efficient method for the synthesis of nitrogen heterocycles containing a cyclic amidine moiety has been developed. The process involves palladium‐catalyzed C(sp2) H activation and isocyanide insertion starting with readily accessible ortho‐heteroarene‐substituted aniline derivatives under mild conditions. 相似文献
An electrophilic amidation via a cationic rhodium(III)‐catalyzed C(sp2) H activation has been developed with the commercially available N‐fluorobenzenesulfonimide as the amino source under external oxidant‐free conditions. This amidation requires only a catalytic amount of base and exhibits excellent functional group tolerance and regioselectivity, providing a new avenue in direct C(sp2) H amidation. 相似文献
A new visible light‐initiated 1,5‐hydride radical shift strategy has been developed to enable the one‐step functionalization of both a C(sp3) Br bond and a C(sp3) H bond adjacent to the same carbon atom. This visible light photoredox catalysis offers a mild and straightforward access to diverse five‐membered carbocyclic ring‐fused polycyclic hydrocarbons with high turnover numbers (TONs; up to 4.93×103) and broad substrate scope.
The direct functionalization of inert sp3 C H bonds is limited to a few bond types. Although the activation of sp3 C H bonds can be accomplished under mild conditions using palladium catalysts, the subsequent functionalization is not trivial due to the high energy required to convert palladium(II) to palladium(IV). We have systematically studied the palladium oxidation using computation‐guided experiments for reactions involving strong chelation control. We find that a mild external ligand could significantly accelerate the oxidation of palladium(II) to palladium(IV) for strong bidentate directing groups. The acceleration is believed to be a result of ligand stabilization of both the palladium(II) and palladium(IV) intermediates.
