Various 1-phenylbut-3-enylidenes, (Ph)CCR2CH=CHR', were generated thermally and photolytically from tosylhydrazone (diazo) precursors. 1,2-Vinyl shifts, leading to 1,3-dienes, R'CH=CHC(Ph)=CR2, were found to predominate over gamma-C-H insertion (R = Me) and to compete with 1,2-H shifts (R = H). Intramolecular addition to the double bond was detected in the case of R = R' = Me. The resulting bicyclobutane is thermally stable and does not mediate the vinyl shift. Stereospecific migration of 1-propenyl groups (R' = Me), with retention of configuration, was observed on thermolysis and direct photolysis of appropriate substrates. These data exclude the intervention of a triplet diradical and point, to vinyl migration in the singlet manifold. Benzophenone-sensitized generation of the carbenes led to partial stereomutation but did not provide conclusive evidence for a triplet rearrangement (isomerization of the diene products could not be avoided under these conditions).
Oxime Radical Promoted Dioxygenation, Oxyamination, and Diamination of Alkenes: Synthesis of Isoxazolines and Cyclic Nitrones
作者:Bing Han、Xiu-Long Yang、Ran Fang、Wei Yu、Chao Wang、Xiao-Yong Duan、Shuai Liu
DOI:10.1002/anie.201203799
日期:2012.8.27
Up the tempo: The intramolecular addition of oxime radicals to CC bonds was achieved by using DEAD and TEMPO to give 4,5‐dihydroisoxazoles as a result of a CO bond‐forming, 5‐exo‐trig cyclization. γ,δ‐Unsaturated ketoximes also reacted to afford cyclicnitrones through CN bond formation. The reactions offer a metal‐free approach for the vicinal difunctionalization of unactivated alkenes.
In Situ Formation of Allyl Ketones via Hiyama−Nozaki Reactions Followed by a Chromium-Mediated Oppenauer Oxidation
作者:Henri S. Schrekker、Martin W. G. de Bolster、Romano V. A. Orru、Ludger A. Wessjohann
DOI:10.1021/jo001750u
日期:2002.4.1
dependent on the substitution pattern of the reaction partners and the reaction conditions. An appropriate choice of these can lead to preferential formation of ketones instead of the alcohols. In addition to its synthetic usefulness, the oxidation-reduction equilibrium is of the utmost importance for the design of enantioselective Hiyama-Nozaki reactions because it is also a potential racemization pathway
Copper-Catalyzed Diamination of Alkenes of Unsaturated Ketohydrazones with Amines
作者:Manman Chen、Li-Jing Wang、Pei-Xing Ren、Xiao-Ying Hou、Zhang Fang、Meng-Nan Han、Wei Li
DOI:10.1021/acs.orglett.7b03401
日期:2018.2.2
A convenient copper-catalyzed intra-/intermoleculardiamination of β,γ-unsaturated hydrazones has been developed with simple amines as external amine sources. The protocol enables efficient access to various nitrogen-containing pyrazolines under mild reaction conditions.
Cu-Catalyzed Aminoacyloxylation of Unactivated Alkenes of Unsaturated Hydrazones with Manifold Carboxylic Acids toward Ester-Functionalized Pyrazolines
作者:Rui-Hua Liu、Zi-Qing Wang、Bang-Yi Wei、Jian-Wu Zhang、Bo Zhou、Bing Han
DOI:10.1021/acs.orglett.8b01507
日期:2018.7.20
A copper-catalyzed aminoacyloxylation of unactivated alkenes of unsaturated hydrazones is achieved by using various commercially available carboxylic acids as the acyloxylating reagents and di-tert-butylperoxide (DTBP) as the oxidant. By using this method, a sequence of structurally diversiform acyloxyl-substituted pyrazolines are efficiently synthesized. Significantly, many carboxyl-containing drugs
Radical-Mediated Diamination of Alkenes with Phenylhydrazine and Azodicarboxylates: Highly Diastereoselective Synthesis of<i>trans</i>-Diamines from Cycloalkenes
作者:Ming-Kui Zhu、Yu-Chen Chen、Teck-Peng Loh
DOI:10.1002/chem.201203832
日期:2013.4.22
Metal‐free synthesis: Diamination of alkenes by using phenylhydrazine and azodicarboxylates could be achieved in a one‐pot manner under very mild conditions (see scheme; Boc=tert‐butoxycarbonyl). This process works with the assistance of acetic acid by means of a radical mechanism and displays a high trans selectivity when cycloalkene substrates were used in the reaction.