Herein, we report a metal-free synthesis of cyclic amidines, oxazines, and an oxazinone under mild conditions by electrophilic amide activation. This strategy features an unusual Umpolung cyclization mode and enables the smooth union of α-aryl amides and diverse alkylazides, effectively rerouting our previously reported α-amination transform.
A method for making diazo-compounds, diazonium salts thereof and other protected forms of these compounds. Diaz-compounds are prepared by reaction of a tertiary phosphine reagent carrying a reactive carbonyl group with an azide. The reaction can also generate an acyl triazene which can be converted thermally or by addition of base to form the diazo-compound or the acyl triazene can be isolated. The method is particularly useful for conversion of azides carrying one or more electron withdrawing groups to diazo-compounds. The method can be carried out in aqueous medium under mild conditions and is particularly useful for conversion of azido sugars to diazo-compound and diazonium salts thereof under physiological conditions. Tertiary phosphine reagents, particularly those that are water-soluble, and precursors for preparation of the reagents are provided.
Asymmetric transfer hydrogenation of α,β-unsaturated, α-tosyloxy and α-substituted ketones
作者:Philip Peach、David J. Cross、Jennifer A. Kenny、Inderjit Mann、Ian Houson、Lynne Campbell、Tim Walsgrove、Martin Wills
DOI:10.1016/j.tet.2005.11.036
日期:2006.2
Asymmetric transferhydrogenation of cyclic and acyclic α,β-unsaturatedketones catalysed by η6-p-cymene/ruthenium(II) and η5-pentamethylcyclopentadienyl/rhodium(III) complexes have been investigated. Cyclicα,β-unsaturatedketones appeared to be more suitable substrates for the synthesis of enantiomerically pure allylic alcohols than do acyclic α,β-unsaturatedketones. A proposed mechanism for the
环状和无环α的不对称转移氢化,β不饱和酮由η催化6 - p -cymene /钌(II)和η 5 -五甲基/铑(III)络合物进行了研究。环状α,β-不饱和酮似乎比无环α,β-不饱和酮更适合用于合成对映体纯的烯丙基醇。讨论了一种由α-甲苯磺酰氧基和卤素取代的苯乙酮形成4-苯基-[1,3]-二氧戊环-2-酮的机理。提出了进一步研究减少α-甲苯磺酰氧基苯乙酮范围和α-取代酮的动态动力学拆分的结果。
α-<i>N</i>-Heteroarylation and α-Azidation of Ketones via Enolonium Species
作者:Atul A. More、Gulab K. Pathe、Keshaba N. Parida、Shimon Maksymenko、Yuriy B. Lipisa、Alex M. Szpilman
DOI:10.1021/acs.joc.7b03058
日期:2018.2.16
Enolonium species, resulting from the umpolung of ketone enolates by Koser’s hypervalentiodinereagents activated by boron trifluoride, react with a variety of nitrogen heterocycles to form α-aminated ketones. The reactions are mild and complete in 4–5 h. Additionally, α-azidation of the enolonium species takes place using trimethylsilyl azide as a convenient source of azide nucleophile.
on the control of diastereoselectivity by H-bond donors. While the squaramide-catalyzed reaction proceeded with a transition state with both squaramide N–H bonds binding to an enolate intermediate, an unprecedented model was proposed for the phosphoramide-mediated reaction wherein an amide N–H bond and an alkylammonium ion formed in situ interact with nitroolefins, with the enolate stabilized by nonclassical