Stereoselective control in the Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents: experimental investigation and theoretical rationalization
Expeditious Synthesis of 2,3,6-Trisubstituted 2H-1,3-Oxazin-4(3H)-ones via the Tertiary Amine-Induced Reaction of 2-Diazo-3-oxoalkanals and Imines Under Mild Conditions
作者:Jiaxi Xu、Hengzhen Qi、Jiantao Zhang
DOI:10.1055/s-0030-1258439
日期:2011.3
A series of 2,3,6-trisubstituted 2H-1,3-oxazin-4(3H)-one derivatives were conveniently synthesized in satisfactory to good yields by the reaction of imines with 2-diazo-3-oxoalkanals in the presence of a catalytic amount of a tertiary amine during several seconds under mild condition. Different bases and α-diazo-β-dicarbonyl compounds were also evaluated and a reaction mechanism is proposed. Compared with the corresponding thermal- and photo-induced reactions, the current method is a metal-free, mild, highly regioselective, and more efficient approach for the synthesis of 2H-1,3-oxazin-4(3H)-one derivatives.
Diazoaldehyde Chemistry. Part 1. Transdiazotization of Acylacetaldehydes in Neutral-to-Acidic Medium. A Direct Approach to the Synthesis of α-Diazo-β-oxoaldehydes
作者:Özkan Sezer、Olcay Anaç
DOI:10.1002/hlca.19940770819
日期:1994.12.14
non-deformylating transdiazotization of acylacetaldehydes was achieved: the reactions of 2-azido-l-ethylpyridinium tetrafluoroborate (4) with acylacetaldehydes 3 proceeded partially without deformylation to yield 16 new α-diazo-β-oxoaldehydes 1 along with diazomethyl ketones 2, especially in the presence of NaOAc (Scheme 1, Tables 1 and 2). The product distribution was substituent-dependent and could
Diazoaldehyde Chemistry. Part 4<i>vilsmeier-haack</i>formylation of diazo compounds: A re-investigation
作者:Özhan Sezer、Kadir Dabak、Olcay Anaç、Ahmet Akar
DOI:10.1002/hlca.19970800327
日期:1997.5.12
Diazomethyl ketones (2-diazoethanones) were reacted with the Vilsmeier reagent ((chloromethylidene)dimethylammonium chloride) to yield α-diazo-β-oxoaldehydes and chloromethyl ketones. 2′,4′-Dimethoxy-α-diazoacetophenone gave 2-chloro-1-(2,4-dimethoxyphenyl)-3-(dimethylamino)prop-2-en-1-one (5) in addition to the expected products. Phenyldiazomethanes gave the corresponding benzyl chlorides but not
Sezer, Oezkan; Hanci, Nalan; Anac, Olcay, Bulletin des Societes Chimiques Belges, 1996, vol. 105, # 5, p. 223 - 226
作者:Sezer, Oezkan、Hanci, Nalan、Anac, Olcay
DOI:——
日期:——
Stereoselective control in the Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents: experimental investigation and theoretical rationalization
作者:Hengzhen Qi、Xinyao Li、Jiaxi Xu
DOI:10.1039/c0ob00783h
日期:——
The stereoselectivity of the Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents was investigated experimentally by determination of the product stereochemistry and theoretically via DFT calculations. The results indicate that imines preferentially attack the less sterically hindered exo-side of the ketenes to generate zwitterionic intermediates. Subsequently, for cyclic imines, the intermediates undergo a conrotatory ring closure directly to produce β-lactams, while for linear imines, the imine moiety of the intermediates isomerizes to more stable intermediates, which further undergo a conrotatory ring closure to afford trans-β-lactams. The steric hindrance and the isomerization, rather than the torquoelectronic effect, play crucial roles in controlling the stereoselectivity in the practical Staudinger reactions involving monosubstituted ketenes with electron acceptor substituents, although the unaccessible borylketene with a powerful electron acceptor group controls the stereoselectivity torquoelectronically, in theory.