A silver catalyzed-cycloisomerization of N-Boc protected ynamides has been developed under mild reaction conditions to provide a wide range of oxazol-2(3H)-ones in good to excellent yields. Moreover, the acid-promoted Pictet-Spengler cyclization of oxazol-2(3H)-ones was described to furnish the corresponding trans-oxazolidones in moderate yields. The heterocycle oxazol-2(3H)-ones have emerged as versatile building blocks for synthetic organic chemists and pharmacologists. 1 Some substituted

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... ol-2(3H)-ones exhibiting herbicidal, antibacterial, antitumor, and neuroleptic activities as well as inhibition against cyclooxygenase-2 have been studied for several decades (Figure 1 ). 2 Additionally, the commercially available Linezolid drug (Zyvox®), containing 2-oxazolidone core structure, has been developed against Gram-positive bacteria. 3 A number of synthetic routes of various substituted oxazol-2(3H)-ones usually involved carbonyl condensation processes to establish the cyclic carbamate moiety. 4 Alternatively, photochemical promoted chlorination 5 and electrochemical oxidation 6 of 2-oxazolidones followed by thermal elimination process have also been studied for the synthesis of various oxazol-2(3H)-ones. Further synthetic applications of oxazol-2(3H)-one derivatives have been demonstrated for the introduction of additional functionalities, such as, substitution at the nitrogen atom by alkylation or acylation, substitution at the carbonyl oxygen by halogenation reaction, and electrophilic addition of the reactive olefin moiety. 7 Therefore, the modifications and transformations for the new types of oxazol-2(3H)-ones to prepare the valuable N-containing heterocycles still remain a challenge.