Efficient Medium Ring Size Bromolactonization Using a Sulfur-Based Zwitterionic Organocatalyst

Abstract

Catalytic bromolactonization of long-chain olefinic acids resulting in the efficient synthesis of medium-sized lactones is reported using a zwitterionic catalyst and stoichiometric N-bromosuccinimide halogen source. The reaction was found to be more efficient at 0 °C than at room temperature, which could be attributed to the temperature dependence of the zwitterionic catalyst.

Computational study on the mechanism of non-catalyzed and catalyzed bromolactonization

“…S4). This is in good agreement with the experimental results that in the presence of Cat, the reaction rate is increased dramatically, and the experimental reaction time is reduced from 54 h to 0.75 h [24,38]. Energies calculated by MP2 method also show the similar results (Fig.…”

“…The addition of 1 and Cat-NBS will proceed via HOMO1-LUMOCat-NBS interaction. This calculation result presents the same phenomenon with the experiment that NBS is first activated by Cat, and then the stable complex Cat-NBS reacts with 1 with the value difference reduced [24].…”

“…After that, a mild and efficient method is found to synthesize medium rings. It is consisted with a zwitterionic as catalyst and stoichiometric N-bromosuccinimide [24] as the halogen donor. 0.75 h is cost to finish the reaction with 99% yield, what's more, the reaction temperature is 0°C which is considered as the appropriate condition.…”

Enantioselective Bromolactonization of Trisubstituted Olefinic Acids Catalyzed by Chiral Pyridyl Phosphoramides

“…We predicted that 1 a might first react with carboxylic acid 2 as a Brønsted base catalyst to form the pyridinium salt A through double hydrogen‐bonding interactions . The initial pyridinium cation in A is first transformed to the dimethylammonium cation and then interacts ionically with the carboxylate anion . The resulting two acidic N−H moieties activate the carbonyl group of NBS in a bidentate manner, arranging 2 and NBS in a proximal position (intermediate B ).…”

4.07 Electrophilic Cyclization

“…116 Very recently, Yeung et al developed the first organocatalytic halolactonization of unsaturated carboxylic acids using zwitterionic catalyst 411 and stoichiometric N-bromosuccinimide halogen source, resulting in the formation of mediumsized lactones (Scheme 110). 117 The Tang group recently discovered a DABCO-catalyzed syn-selective 1,4-bromolactonization of enynes. This reaction gave axially chiral allenes as the main products.…”