Study On Yb?OTf?₃-mediated Access To Furans & Passerini Reaction Under The Auxiliary Of Water

Furans, one class of the most significant five-membered heterocycles, could be found in many naturally occurring compounds. Polysubstituted furans can also be employed as building blocks for the total synthesis of complicated naturally occurring metabolites, and as versatile starting materials for the preparation of a variety of heterocyclic and acyclic compounds. An effective approach to the synthesis of functionalized furans is through the transition metal-catalyzed cyclization of unsaturated compounds. While these reactions are useful, most of them still need improvement in terms of catalyst loadings, yields, scope limitations, and/or vigorous reaction conditions.In chapter one, various synthetic routes to furan derivatives in recent literature were generally reviewed, and the extensive applications in organic synthesis of Eschenmoser sul?de contraction reaction, Yb(OTf)3 as Lewis acid catalyst, ?-ketothioamides, and arylglyoxals were successively described followed.An Yb(OTf)3-promoted tandem synthesis of highly substituted furan derivatives from KTAs and arylglyoxals at room temperature has been developed. The optimal reaction conditions were established by employing KTAs and arylglyoxals in a ratio of 1 : 1.2 with a stoichiometric amount of Yb(OTf)3 in CH3 CN at room temperature. By testing various KTAs and arylglyoxals, a large scope of substrates were found to be tolerated well. Furthermore, LC-MS were performed on the reaction process to trace key intramediates and scanning electron microscope(SEM)- energy dispersive X-ray spectrometer(EDS) analysis were conducted to confirm the contraction of sul?de, based on which the possible mechanism was proposed eventually. This mild and rapid approach can achieve good yields with convenient operation and excellent selectivity, on which no leterature was reported previously.The structures of all the newly synthesized compounds were characterized by 1H NMR, 13 C NMR, and HRMS. Single crystal of compound 3aa was cultured and its precise configuration was determined.The significant applications and plausible mechanisms involved in Passerini reactions were briefly presented in chapter three. Subsequently, an efficient and facile protocol for the synthesis of the Passerini adducts ?-acyloxycarboxamides was established. Through a series of control experiments on the dosage of water added, the optimal proportion of aldehydes, isocyanides and water was determined in a molecular ratio of 3 : 1 : 3, implying the role of water as a reactant in the transformation. The possible mechanism for the reaction was further confirmed by this result and following H218 O isotope labeling experiments.