Merging Jørgensen's and MacMillan's organocatalytic aldehyde chlorinations enables the synthesis of chiral vinylcyclopropanes and (-)-cis-aerangis lactone via terpene-derived 1,2-epoxides.
An oxidation of allylic and benzylic alcohols to the corresponding carboxylic acids is effected by merging a Cu-catalyzed oxidation using O2 as a terminal oxidant with a subsequent chlorite oxidation (Lindgren oxidation). The protocol was optimized to obtain pure products without chromatography or crystallization. Interception at the aldehyde stage allowed for Z/E-isomerization, thus rendering the oxidation stereoconvergent with respect to the configuration of the starting material.
Oxidation of allylic and benzylic alcohols (I), (III) and (VII) to the corresponding carboxylic acids (V), (VI), and (IX) is achieved by merging a Cu-catalyzed oxidation using dioxygen as a terminal oxidant with subsequent chlorite oxidation. The protocol is optimized to obtain pure products without the need of further purification. Interception at the aldehyde stage allows for Z/E-isomerization. -(KOENNING, D.; OLBRISCH, T.; SYPASEUTH, F. D.; TZSCHUCKE, C. C.; CHRISTMANN*, M.; Chem. Commun. (Cambridge) 50 (2014) 39, 5014-5016, http://dx.
Transforming Terpene-Derived Aldehydes into 1,2-Epoxides via Asymmetric α-Chlorination: Subsequent Epoxide Opening with Carbon Nucleophiles. -A practical protocol for the conversion of aldehydes (I) into terminal epoxides (II) via an organocatalytic asymmetric enamine chlorination is described. If desired or nessessary, the reaction sequence can be stopped at the chloroalcohol, for example (IV).In addition, a stereoselective rearrangement of 1,2-epoxy-4Z-alkenes (IIb) and (IId) into cyclopropanes (VI) and (VII) is found. Interestingly, derivatives bearing a trisubstituted double bond with (E)-configuration, such as (IIc) affords the cyclopropanes only as 1 : 1 diastereomeric mixture. The methodology is applied to a short synthesis of (-)-aerangis lactone (XI). -(WINTER, P.; SWATSCHEK, J.; WILLOT, M.; RADTKE, L.; OLBRISCH, T.; SCHAEFER, A.; CHRISTMANN*, M.; Chem. Commun. (Cambridge) 47 (2011) 44, 12200-12202, http://dx.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.