An enantioselective intramolecular oxidative cyclization of 4-alkenoic acids was developed. The reaction proceeded via a π-allyl Pd intermediate generated by an allylic C–H activation to give γ-lactone derivatives with moderate to good enantioselectivity. Spiro bis(isoxazoline) ligand, SPRIX, was indispensable for this asymmetric transformation.
Palladium-Catalyzed Carbonylative Heck-Type Reactions of Alkyl Iodides
作者:Kayla S. Bloome、Erik J. Alexanian
DOI:10.1021/ja1053913
日期:2010.9.22
A palladium-catalyzed carbonylative Heck-type cyclization of alkyl halides is described. Treatment of a range of primary and secondary alkyliodides with catalytic palladium(0) under CO pressure forms a variety of synthetically versatile enone products. The reactivity described represents a rare example of a palladium-catalyzedHeck-type cyclization involving unactivatedalkyl halides with β-hydrogens
描述了烷基卤化物的钯催化羰基化 Heck 型环化。在 CO 压力下用催化钯 (0) 处理一系列伯和仲烷基碘,形成各种合成通用的烯酮产品。所描述的反应性代表了钯催化的 Heck 型环化的一个罕见例子,涉及未活化的烷基卤与 β-氢。烯烃取代具有良好的耐受性,并且可以轻松获得单环和双环碳环。
Iron-catalyzed ring-opening of cyclic carboxylic acids enabled by photoinduced ligand-to-metal charge transfer
of 1,n-dicarbonyl compounds through the homolytic C–C bond cleavage of unstrained carbocyclic and heterocyclic ring systems. This method exhibits a lot of synthetic advantages including mild conditions, simple operation, and convenience of amplification. Mechanistic studies support the generation of peroxy radical species via oxygen capture followed by radical fragmentation.
in good yields by intramolecular hydroamination of N-alkoxy ureas in the presence of an organic photocatalyst and an inorganic base. In this reaction, the N-alkoxy urea anion generated by deprotonation undergoes photocatalyzed single-electron-transfer oxidation to generate the correspondingradical, which cyclizes to afford the imidazolinone ring. This new protocol grants access to an array of complex
Intramolecular nucleophilic acyl substitution reactions of halo-substituted esters and lactones. New applications of organosamarium reagents
作者:Gary A. Molander、Jeffrey A. McKie
DOI:10.1021/jo00077a053
日期:1993.12
Intramolecular nucleophilic acyl substitution reactions involving a broad range of halo substituted carboxylic acid derivatives have been accomplished in excellent yield employing samarium(II) iodide as the reductive coupling agent. Although particular substrates cyclized most effectively in THF in the presence of tripiperidinophosphine oxide, carboxylic acid esters, the focus of this report, cyclize equally well without such an additive in the presence of a catalytic quantity of iron(III) complexes. Thus a comprehensive series of halo substituted esters were cyclized in excellent yield to the corresponding 4-, 5-, and 6-membered carbocycles. The reaction is extremely mild and selective as demonstrated by experiments wherein alkyl chlorides, acetals, and olefins remain completely intact under the reaction conditions. In addition to introducing a convenient procedure for preparing stereodefined spirocyclic systems, a new ring expansion sequence has been developed that appears extremely general for the preparation of various ring systems.