21019-55-6Relevant articles and documents
Vibrational Circular Dichroism of Optically Active Cyclopropanes. Experimental Results
Heintz, V. J.,Keiderling, T. A.
, p. 2395 - 2403 (1981)
The vibrational circular dichroism spectra of several trans-1,2-disubstituted cyclopropanes between 3200 and 1250 cm-1 are presented.Isotopic substitutions allowed assignments of many of the VCD bands to specific CH stretching or bending modes.
Stereodivergent Rhodium(III)-Catalyzed cis-Cyclopropanation Enabled by Multivariate Optimization
Piou, Tiffany,Romanov-Michailidis, Fedor,Ashley, Melissa A.,Romanova-Michaelides, Maria,Rovis, Tomislav
supporting information, p. 9587 - 9593 (2018/08/07)
The design of stereodivergent transformations is of great interest to the synthetic community as it allows funneling of a given reaction pathway toward one stereochemical outcome or another by only minor adjustments of the reaction setup. Herein, we present a physical organic approach to invert the sense of induction in diastereoselective cyclopropanation of alkenes with N-enoxyphthalimides through rhodium(III) catalysis. Careful parametrization of catalyst-substrate molecular determinants allowed us to interrogate linear-free energy relationships and establish an intuitive and robust statistical model that correlates an extensive number of data points in high accuracy. Our multivariate correlations-steered mechanistic investigation culminated with a robust and general diastereodivergent cyclopropanation tool where the switch from trans- to cis-diastereoinduction is attributed to a mechanistic dichotomy. Selectivity might be determined by the flexibility of rhodacyclic intermediates derived from ring-opened versus -unopened phthalimides, induced by both their respective ring size and the Sterimol B1 parameter of the CpX ligand on rhodium.
The direct preparation of functionalised cyclopropanes from allylic alcohols or α-hydroxyketones using tandem oxidation processes
McAllister, Graeme D.,Oswald, Magalie F.,Paxton, Richard J.,Raw, Steven A.,Taylor, Richard J.K.
, p. 6681 - 6694 (2007/10/03)
New manganese dioxide-mediated tandem oxidation processes (TOPs) have been developed, which facilitate the direct conversion of allylic alcohols and α-hydroxyketones into polysubstituted functionalised cyclopropanes. In the simplest version, the oxidation of an allylic alcohol is carried out in the presence of a stabilised sulfurane, and the intermediate α,β-unsaturated carbonyl compound undergoes in situ cyclopropanation. By using a combination of stabilised phosphorane and sulfurane, the direct conversion of allylic alcohols or α-hydroxyketones into functionalised cyclopropanes is achieved, with in situ cyclopropanation being followed by Wittig olefination, or vice versa. The application of these methods to a formal synthesis of the lignan (±)-picropodophyllone, and to novel analogues of the insecticide allethrin II, is described.
