(R)-(+)-[VCD(-)984]-4-Ethyl-4-methyloctane: A Cryptochiral Hydrocarbon with a Quaternary Chiral Center. (2) Vibrational CD Spectra of Both Enantiomers and Absolute Configurational Assignment
the VCD spectral curves were mirror images of each other. Based on the observed positive VCD band at 984 cm -1 for (S)-(-)-1, its absoluteconfiguration was fully designated as (S)-(-)-[VCD(+)984]-1. The VCD spectrum was quantum chemically calculated by the DFT MO method at the B3PW91/6-31G(d,p) level, and the simulated VCD curve for (S)-1 agreed very well with the observed VCD spectrum of (S)-(-)-1
Rhodium-Catalyzed C−C Bond Cleavage: Construction of Acyclic Methyl Substituted Quaternary Stereogenic Centers
作者:Tobias Seiser、Nicolai Cramer
DOI:10.1021/ja101469t
日期:2010.4.21
A rhodium-catalyzed enantioselective insertion into the C-C bond of tert-cyclobutanols and subsequent proto-demetalation provides access to methyl substituted quaternary stereogenic centers in excellent yields and enantioselectivities. The reaction was used for a synthesis of (S)-4-ethyl-4-methyl-octane, the simplest saturated hydrocarbon with a quaternary stereogenic center.
Zirconocene-Mediated Selective C–C Bond Cleavage of Strained Carbocycles: Scope and Mechanism
作者:Jeffrey Bruffaerts、Alexandre Vasseur、Sukhdev Singh、Ahmad Masarwa、Dorian Didier、Liron Oskar、Lionel Perrin、Odile Eisenstein、Ilan Marek
DOI:10.1021/acs.joc.7b03115
日期:2018.4.6
Several approaches using organozirconocene species for the remote cleavage of strained three-membered ring carbocycles are described. ω-Ene polysubstituted cyclopropanes, alkylidenecyclopropanes, ω-ene spiro[2.2]pentanes, and ω-ene cyclopropyl methyl ethers were successfully transformed into stereodefined organometallic intermediates, allowing an easy access to highly stereoenriched acyclic scaffolds