Direct access to functionalized benzotropones, azepanes, and piperidines by reductive cross-coupling of α-bromo enones with α-bromo enamides
作者:Timothy K. Beng、Kayla Sincavage、Ann Wens V. Silaire、Amir Alwali、Daniel P. Bassler、Laura E. Spence、Oliver Beale
DOI:10.1039/c5ob00517e
日期:——
The synthesis of functionalized azepenes and piperidines bearing an α-cycloheptenone or benzotropone derivative has been accomplished through direct reductive cross-coupling of α-bromo eneformamides or enecarbamates with highly versatile α-bromo benzotropone derivatives, under cobalt catalysis. The coupling products have been further elaborated to other synthetically useful aza-heterocyclic frameworks
Palladium-catalyzed reactions of various 2-bromo-3-exo-methylenecycloalkenes with a stabilized nucleophile were examined. When the carbocycles were nine-membered or larger, the corresponding endocyclic allenes were isolated in excellent yields. In a reaction of the eight-membered cyclic substrate, initial formation of a cycloocta-1,2-diene derivative was detected; however, it dimerized slowly. The
Cascade Cyclization via a 4-<i>exo</i>-<i>dig</i>-Cyclocarbopalladation for an Easy Access to New Polycyclic Structures
作者:Jean Suffert、Bahaâ Salem、Philippe Klotz
DOI:10.1055/s-2003-44360
日期:——
The 5-exo-dig-cyclocarbopalladation is a known reaction although the functionality present on the substrates used is generally limited. This reaction was performed on our original substrates propargylic diols 2a-c and 3a-c gave encouraging results. Once the analogs α-bromopropargylic diols were used, the 4-exo-dig-cyclocarbopalladation turns out to be a new possible way to prepare bicyclic compounds containing a strained 1,2-cyclobutanediol. This process is associated with a Stille cross-coupling that can be ended in some cases by a 6Ï-electrocyclization. This reaction sequence can thus achieve an increase in structural complexity from readily available starting materials, in a one-pot operation.
A Direct Organocatalytic Enantioselective Route to Functionalized
<i>trans</i>
‐Diels–Alder Products Having the Norcarane Scaffold
作者:Casper L. Barløse、Niklas L. Østergaard、René S. Bitsch、Marc V. Iversen、Karl Anker Jørgensen
DOI:10.1002/anie.202106598
日期:2021.8.9
organocatalysis with excellent selectivity, high yield and up to five contiguous stereocenters is presented. The reaction concept integrates the halogen effect and a novel discovered pseudo-halogen effect to direct an endo-selective, secondary-amine catalyzed Diels–Alder reaction allowing for the subsequent formation of trans-Diels–Alder cycloadducts featuring the norcarene scaffold. The methodology relies on
Chiral aziridination of cyclic α-bromoenones is achieved by the use of the lithium salt of (S S )-(+)-p-toluenesulfinamide, which leads to products with diastereomeric excesses in the range of 30―65% using a simple protocol. A key factor associated with chiral induction is the incorporation of the reacting olefin in a cycle, indicating the importance of conformational restriction in the reacting double