Electronic Activity Tuning of Acyclic Guanidines for Lactide Polymerization
摘要:
Novel aromatic guanidine-based organocatalysts for the ring-opening of L-lactide were synthesized and applied in comprehensive polymerization experiments and kinetic studies. The introduction of electronically active substituents led to a significant change in activity by 2 orders of magnitude. The formed polylactide is featured with narrow polydispersity and high end-group fidelity, both characteristics that are typical for living polymerizations. Besides that, using linear free-energy relationships and DFT calculations revealed new insights into the polymerization mechanism. The formation of an adduct consisting of the catalyst and initiator/chain end turned out to be the rate-limiting step.
In this work, we developed the catalytic guanylation of thiourea using Ru(bpy)3Cl2 as a photocatalyst under irradiation by visible light. The conversion of various thioureas to the corresponding guanidines was achieved using 1–5 mol % of photocatalyst in a mixture of water and ethanol at room temperature. Key benefits of this reaction include the use of photoredox catalyst, low-toxicity solvents/base
Metal-free synthesis of guanidinesfrom thioureas under visible-light irradiation in water was successfully developed. Using 1–5 mol% of inexpensive and commercially available phenazine ethosulfate as a photocatalyst in the presence of 1 wt% cetyltrimethylammonium bromide (CTAB) as surfactant with K2CO3 as an additive base, transformations of a variety of thioureas into the corresponding guanidines under
成功开发了在水中可见光照射下从硫脲中无金属合成胍类化合物。使用 1-5 mol% 廉价且可商购的吩嗪乙硫酸盐作为光催化剂,在 1 wt% 十六烷基三甲基溴化铵 (CTAB) 作为表面活性剂的情况下,以 K 2 CO 3作为添加基,将各种硫脲转化为相应的胍在可见光照射下可获得中高产率。该反应的优点包括使用无金属光催化剂、水作为无毒溶剂以及易于在室温下以开瓶方式操作。
Electrochemical NaI-mediated one-pot synthesis of guanidines from isothiocyanates <i>via</i> tandem addition-guanylation
conditions, we successfully demonstrated the formation of 30 different guanidine compounds, achieving yields ranging from fair to excellent. Furthermore, the synthesis method could be carried out on a gram scale with a good yield. This protocol stands out for its cost-effectiveness, step-economical design, high tolerance towards various functional groups, and environmentally friendly reaction conditions