Spiro-fused 2-alkoxy-2-amino-Δ<sup>3</sup>-1,3,4-oxadiazolines. Synthesis and thermolysis to corresponding aminooxycarbenes
作者:Philippe Couture、John Warkentin
DOI:10.1139/v97-153
日期:1997.9.1
undergo thermolysis in benzene at 90 °C with first-order rate constants of (1.6–50) × 10−5 s−1. The dependence of these rate constants on the nature of the substituents present on the oxadiazoline ring is consistent with a mechanism involving a carbonylylideintermediate. Substituents on N of the oxazolidine or tetrahydro-1,3-oxazine moieties play a major role in determining the fragmentation pathways
hydantoins. Major products from the reactions of the N-carbonyl carbenes with dimethyl acetylenedicarboxylate or with methyl propiolate were 2-oxazolines resulting from apparent acyl transfers from N to C in the proposed dipolar intermediates; minor products of 1:2 (carbene:trap) stoichiometry were also observed. Keywords: nucleophilic carbene, aminooxycarbene, oxadiazoline, amide rotation, oxazolidine
Δ3-1,3,4-恶二唑啉在苯中在 90°C 下热解产生的一系列恶唑烷-2-亚基和一个四氢-1,3-恶嗪-2-亚基通过插入 OH 键被截获酚类。在两种情况下,初始产物重排为 N-(2-芳氧基乙基)-N-甲基甲酰胺。围绕这些最终产物的酰胺 CN 键旋转的活化能测量为 20.4 kcal/mol。氨基氧卡宾与两当量的异氰酸甲酯或苯基酯反应生成螺合乙内酰脲。N-羰基卡宾与乙炔二甲酸二甲酯或丙炔酸甲酯反应的主要产物是 2-恶唑啉,这是由拟议的偶极中间体中从 N 到 C 的明显酰基转移产生的;还观察到 1:2(卡宾:陷阱)化学计量的次要产物。关键词:亲核卡宾,
Non-stabilized diazoalkane synthesis <i>via</i> the oxidation of free hydrazones by iodosylbenzene and application in <i>in situ</i> MIRC cyclopropanation
作者:Emmanuelle M. D. Allouche、André B. Charette
DOI:10.1039/c8sc05558k
日期:——
powerful reagents in organic synthesis, but the risks associated with their toxicity and instability often limit their uses. Herein we describe an efficient, easy-to-handle and safe batch protocol for the in situ generation and cyclopropanation of these highly reactive non-stabilized diazoalkanes through the oxidation of free hydrazones using iodosylbenzene. Numerous substituted cyclopropanes have been
Site selectivity in the reactions of 1,3-dipoles with norbornadiene derivatives
作者:D. Cristina、M. De Amici、C. De Micheli、R. Gandolfi
DOI:10.1016/s0040-4020(01)92451-2
日期:1981.1
2-diazopropane and C-pnenyl-N-methyl-nitrone react with the sole tetrasubstituted double bond of 1a–c in stereo- and site-specific cycloadditions. The quantitative evaluation of the two possible reaction paths was performed by glc analysis. The compounds detected were those arising from Diels-Alder cycloreversions of the thermally labile intermediate adducts 2 and 3 (Scheme 1). The results were rationalized
Safe and Facile Access to Nonstabilized Diazoalkanes Using Continuous Flow Technology
作者:Pauline Rullière、Guillaume Benoit、Emmanuelle M. D. Allouche、André B. Charette
DOI:10.1002/anie.201802092
日期:2018.5.14
potential of nonstabilized diazo compounds, their utilization has always been hampered by stability, toxicity, and safety issues. The present method opens up access to the most reactive nonstabilized diazoalkanes. Among diazo compounds, nonstabilized alkyl diazo compounds are the least represented because of their propensity to degrade during preparation. The continuous flow oxidation process of hydrazones