5014-83-5Relevant articles and documents
(Enantio)selective Hydrogen Autotransfer: Ruthenium-Catalyzed Synthesis of Oxazolidin-2-ones from Urea and Diols
Pe?a-López, Miguel,Neumann, Helfried,Beller, Matthias
supporting information, p. 7826 - 7830 (2016/07/07)
A novel strategy for the synthesis of oxazolidin-2-ones from vicinal diols and urea is described. In this heterocycle synthesis, two different C?O and C?N bonds are sequentially formed in a domino process consisting of nucleophilic substitution and alcohol amination. The use of readily available starting materials and the good atom economy render this process environmentally benign. While this transformation is already highly chemo- and regioselective, we also developed the first asymmetric version of this method using (R)-(+)-MeO-BIPHEP as the chiral ligand.
Substituted Oxazoles: Synthesis via Lithio Intermediates
Whitney, Scott E.,Rickborn, Bruce
, p. 3058 - 3063 (2007/10/02)
Reactions of 2-α-, 2-, 4-, and 5-lithiooxazoles are used to prepare various substituted derivatives.Previously unrecognized time dependence for the reaction of a 2-lithiooxazole with benzaldhyde is described, and a rationale for this behavior is offered.Competitive reactions occur when the readily available 2,5-diphenyloxazole is treated with n-butyllithium.Deprotonation of the ortho position of the 2-phenyl group and addition of n-butyl to the 2-position of the oxazole compete with the desired 4-lithiation.The use of sec-butyllithium/catalytic lithium tetramethylpiperidide allows preferential formation of 4-lithio-2,5-diphenyloxazole.This intermediate has been converted to the 4-bromo, -methyl, -hydroxybenzyl, -benzoyl, and -trialkylsilyl derivatives.Lithiation of 2,4-diphenyloxazole and subsequent trimethylsilylation occur readily at the 5-position.Deprotonation of 2-alkyloxazoles occurs at the α-carbon in preference to ring sites.Further reaction of an α-phenyl-2-oxazolemethanol methoxymethyl ether with base and acetyl chloride leads to an acyloin derivative.Chromic acid oxidation is used to prepare both 2- and 4-benzoyloxazoles.The formation of an 2-ethoxyoxazole from 2-oxazolone vis Meerwein salt chemistry is described.
Studies Dealing with the Aza-Claisen Rearrangement of 2-Allyloxy-Substituted Oxazoles
Padwa, Albert,Cohen, Leslie A.
, p. 399 - 406 (2007/10/02)
The scope of the thermal -sigmatropic rearrangement of a number of 2-allyloxy-substituted 4,5-diphenyloxazoles has been examined.These systems undergo a facile aza-Claisen rearrangement to give 3-allyl-substituted 4,5-diphenyl-4-oxazolin-2-ones.In contrast to the thermal results, irradiation of the 2-allyloxy- or benzyloxy-substituted oxazole gave rise to a mixture of 3- and 5-substituted oxazolinones.The photolysis proceeds via C-O bond scission to generate a radical pair which subsequently recombines to produce the mixture of oxazolinones.A series of related oxazoles was prepared in which the heterocyclic ring and the ? bond are connected by an alkoxy side chain.All attempts to induce an intramolecular Diels-Alder reaction failed.The only product that could be obtained corresponds to that derived from an intramolecular ene reaction.The excited-state behavior of several 2- and 5-allyloxy-substituted oxazoles was also studied.The rationale for the difference in thermal and photochemical behavior is discussed.
