46047-24-9Relevant articles and documents
Reaction Conditions for the Regiodivergent Direct Arylations at C2- or C5-Positions of Oxazoles using Phosphine-Free Palladium Catalysts
Shi, Xinzhe,Soulé, Jean-Fran?ois,Doucet, Henri
, p. 4748 - 4760 (2019/09/12)
Two sets of reaction conditions for the regiodivergent C2- or C5- direct arylations of oxazole are reported. In both cases, phosphine-free catalysts and inexpensive bases were employed allowing the access to the arylated oxazoles in moderate to high yields. Using Pd(OAc)2/KOAc as catalyst and base, regioselective C5-arylations were observed; whereas, using Pd(acac)2/Cs2CO3 system, the arylation occurred at the C2-position of oxazole. The higher reactivity of C5-H bond of oxazole as compared to the C2-H bond in the presence of Pd(OAc)2/KOAc system is consistent with a concerted metalation deprotonation mechanism; whereas the C2-arylation likely occurs via a simple base deprotonation of the oxazole C2-position. Then, from these C2- or C5-arylated oxazoles, a second palladium-catalyzed direct C?H bond arylation affords 2,5-diaryloxazoles with two different aryl groups. We also applied these sequential arylations to the straightforward synthesis of 2-arylphenanthro[9,10-d]oxazoles via three C?H bond functionalization steps. The Ru-catalyzed C?H arylation of the aryl unit of 2-aryloxazoles is also described. (Figure presented.).
DDQ-induced dehydrogenation of heterocycles for c-c double bond formation: Synthesis of 2-thiazoles and 2-oxazoles
Li, Xiangnan,Li, Cheng,Yin, Bing,Li, Cong,Liu, Ping,Li, Jianli,Shi, Zhen
, p. 1408 - 1411 (2013/07/26)
Strong as an Ox: 2-Thiazoles and 2-oxazoles are formed by oxidation of 2-thiazolines and 2-oxazolines without requiring substituents at the C4 and C5 positions. DDQ plays an important role as the oxidant in this transformation and metal is unnecessary. This general procedure shows good functional group tolerance and provides a wide variety of 2-thiazoles and 2-oxazoles in moderate to excellent yields.
Anodic methoxylation and acetoxylation of imines and imidates
Baba, Daisuke,Fuchigami, Toshio
, p. 3133 - 3136 (2007/10/03)
Anodic oxidation of cyclic imidates, 2-aryl-2-oxazolines, in methanol provided the corresponding 4-methoxylated products. Anodic α-methoxylation and α-acetoxylation of open-chain imines derived from glycine esters and benzophenone were also achieved using a bromide ion mediator. On the other hand, anodic α-acetoxylation of CF3-containing imine and imidate was successful without use of the bromine mediator. This is the first example of successful anodic α-substitution of imines and imidates.