A Facile Access to 3,5-Disubstituted Oxazolones Featuring a Cu-catalyzed Cyclization of N-Alkynyl tert-Butyl Carbamates

Abstract

Using cheap and readily accessible CuCl as the catalyst, an operationally simple and efficient method for the synthesis of 3,5-disubstituted oxazolones has been realized by the cyclization of N-alkynyl tert-butyl carbamates. The reaction proceeds under mild reaction conditions and shows good functional group compatibility.

Controlled Synthesis of 1,3,5-Oxadiazin-2-ones and Oxazolones through Regioselective Iodocyclization of Ynamides

“…Thus, tremendous efforts have been devoted to the development of versatile methods for constructing these cyclic carbamates. And the most general method focuses on the cyclization of different types of starting materials, such as N -Boc-protected alkynyl amines, N -alkynyl tert -butyloxycarbamates, and others . Given the great importance of electrophilic iodocyclization, development of a practical, efficient iodocyclization for the preparation of these target cyclic carbamates is highly desirable.…”

“…Ynamides and their derivatives are versatile building blocks in organic synthesis . For example, transition metal (e.g., Au, Pd, Cu) catalyzed cycloisomerization of the N -alkynyl tert -butyloxy­carbamates is an efficient approach to the synthesis of polysubstituted oxazolones . Keeping the importance of electrophilic iodocyclization in mind, we hoped to investigate whether such a cycloisomerization could be mediated by less expensive and less toxic iodine-containing reagents.…”

Palladium-Catalyzed Direct Alkenylation of 2-Oxazolones: An Entry to 3,4,5-Trisubstituted 2-Oxazolones

“…Lautens and co-workers found that 3,5-disubstituted 2-oxazolones could be efficiently assembled by the Pd-catalyzed coupling of β,β-dibromoenamides with boronic acids . Recently, a dichotomy protocol for the access of 3,5-disubstituted or 3,4,5-trisubstituted 2-oxazolones featuring the Pd-catalyzed cycloisomerization of N -alkynyl tert -butyloxycarbamates has been realized in our group; however, as for the latter case, only 4-allyl-2-oxazolones could be synthesized, and the development of a general as well as efficient method for the synthesis of 3,4,5-trisubstituted 2-oxazolones both remains challenging and has great value.…”

“…As such, the effective synthesis of 4-alkenyl-2-oxazolones constitutes an unmet goal. To address this issue, we hypothesized that the Pd-catalyzed direct alkenylation of 2-oxazolones would provide an operationally simple as well as atom- and step-economical route to 4-alkenyl-2-oxazolones (Scheme , eq 2), thus providing a complementary method to our attempts , to elaborate polysubstituted 2-oxazolones. Herein, we report such a reaction.…”

A Convenient Access to Functionalized Oxazol-2-One-5-Carboxylates from β-Aminoalcohols Through NBS-Light Mediated Oxidation of Cis- or Trans-N-Alkyloxazolidinones

“…Oxazolones can also be conveniently obtained by a one pot Ugi four-component reaction [45]. The metalcyclization (e.g., Au, Pd, Cu and Rh) of ynamide derivatives such as N-alkynyl tert-butyloxycarbamates is considered to be one of the most effective strategies for the construction of these structures [23,[46][47][48][49][50][51]. Recently, the Zhu group described a transition metal-free cyclization of N-alkynyl tert-butyloxycarbamates [22] giving oxazolones by using NIS-K 2 CO 3 conditions.…”