Elimination reactions of terminal .beta.-oxy selenoxides. Synthesis of aryl and vinyl enol ethers and of furans, oxazoles, and thiazoles
摘要:
Elimination reactions of terminal selenoxides holding an alkoxy group in the beta position, RCH-(OR)CH2SeOPh, are usually difficult and can give rise to complex reaction mixtures. We report that these reactions take place more easily whenever the oxygen atom is linked to an unsaturated group (-CH=CHR, -Ar, -CR=O, -CH=NR). These selenoxides are easily available, and the elimination reaction was employed to effect useful syntheses of both open-chain and cyclic aryl and vinyl enol ethers. Moreover, by simple isomerization with acids or bases the cyclic derivatives can be transformed into the corresponding furans. The same procedure has been employed to synthesize substituted oxazoles and thiazoles also.
Cyclization of Propargylic Amides: Mild Access to Oxazole Derivatives
作者:Jan P. Weyrauch、A. Stephen K. Hashmi、Andreas Schuster、Tobias Hengst、Stefanie Schetter、Anna Littmann、Matthias Rudolph、Melissa Hamzic、Jorge Visus、Frank Rominger、Wolfgang Frey、Jan W. Bats
DOI:10.1002/chem.200902472
日期:2010.1.18
the oxazole synthesis were developed and chelate ligands can be obtained. The use of Barluenga’s reagent offers a new and mild access to the synthetically valuable iodoalkylideneoxazoles from propargylicamides, this reagent being superior to other sources of halogens.
A photoredox-catalyzed radical addition of methylene-2-oxazolines has been developed under visible light irradiation to synthesize monofluorooxazoles with quaternary C–F centers using 2-bromo-2-fluoro-3-oxo-3-phenylpropionates as radical source.
Oxazoles are pivotal structural scaffolds in coordination chemistry, natural products, medicinal chemistry, and material science.[1] Consequently, the synthesis of functionalized oxazoles with multiple pharmacological and biological properties has become the subject of intense research in recent decades.[2] The difluoromethylene group (CF2), which is a bioisostere for an oxygen atom, can significantly
作者:Xi‐Jia Liu、Chao Zheng、Yi‐Han Yang、Shicheng Jin、Shu‐Li You
DOI:10.1002/anie.201904156
日期:2019.7.29
Described herein is an asymmetric allylic aromatization (AAAr) strategy that employs readily accessible equivalents of benzylic nucleophiles in iridium‐catalyzed allylic substitution reactions with the concomitant formation of aromatic rings by aromatization. The optimized reaction conditions involving a catalyst derived from a commercially available iridium precursor and the Carreira ligand are compatible
Efficient Cycloisomerization of Propargyl Amides by Electrophilic Gold(I) Complexes of KITPHOS Monophosphines: A Comparative Study
作者:Simon Doherty、Julian G. Knight、A. Stephen K. Hashmi、Catherine H. Smyth、Nicholas A. B. Ward、Katharine J. Robson、Sophie Tweedley、Ross W. Harrington、William Clegg
DOI:10.1021/om1006769
日期:2010.9.27
Electrophilic gold(I) complexes of diphenyl- and dicyclohexylphosphino-based KITPHOSmonophosphines catalyze the 5-exo-dig cycloisomerization of a range of propargyl amides to afford the corresponding alkylidene oxazolines; in all cases catalysts formed from diphenylphosphino-substituted KITPHOSmonophosphines outperformed their dicyclohexylphosphino counterparts as well as that based on triphenylphosphine