180322-87-6Relevant academic research and scientific papers
Expanding Stereoelectronic Limits of endo- tet Cyclizations: Synthesis of Benz[ b]azepines from Donor-Acceptor Cyclopropanes
Vartanova, Anna E.,Plodukhin, Andrey Yu.,Ratmanova, Nina K.,Andreev, Ivan A.,Anisimov, Mikhail N.,Gudimchuk, Nikita B.,Rybakov, Victor B.,Levina, Irina I.,Ivanova, Olga A.,Trushkov, Igor V.,Alabugin, Igor V.
, p. 13952 - 13961 (2021)
The importance of intramolecular constraints in cyclic transition-state geometries is especially pronounced in n-endo-tet cyclizations, where the usual backside approach of a nucleophile to the breaking bond is impossible for the rings containing less than eight atoms. Herein, we expand the limits of endo-tet cyclizations and show that donor-acceptor cyclopropanes can provide a seven-membered ring via a genuine 6-endo-tet process. Substrates containing a N-alkyl-N-arylcarbamoyl moiety as an acceptor group undergo Lewis acid-induced cyclization to form tetrahydrobenz[b]azepin-2-ones in high yields. The reaction proceeds with the inversion of the configuration at the electrophilic carbon. In this process, a formally six-membered transition state yields a seven-membered ring as the pre-existing cycle is merged into the forming ring. The stereochemistry of the products can be controlled by the reaction time and by the nature of Lewis acid, opening access to both diastereomers by tuning of the reaction conditions.
Preparation of both enantiomers of cyclopropane derivatives from the reaction of vinyl selenones with di-(-)-bornyl malonate
Bagnoli, Luana,Scarponi, Catalina,Testaferri, Lorenzo,Tiecco, Marcello
scheme or table, p. 1506 - 1514 (2009/12/01)
The reaction of vinyl selenones with di-(-)-bornyl malonate and sodium hydride occurred with low diastereoselectivity and afforded a mixture of two diastereomeric cyclopropane derivatives in comparable yields. These, however, could be easily separated by chromatography. Removal of the bornyl group afforded highly enantiomerically enriched cyclopropanes. An example of the simple conversions of these cyclopropanes into useful cyclopropane α-amino acids is also illustrated. The syntheses of several vinyl selenides and selenones are also described.
Asymmetric cyclopropanations by rhodium(II) N-(arylsulfonyl)prolinate catalyzed decomposition of vinyldiazomethanes in the presence of alkenes. Practical enantioselective synthesis of the four stereoisomers of 2-phenylcyclopropan-1-amino acid
Davies, Huw M. L.,Bruzinski, Paul R.,Lake, Debra H.,Kong, Norman,Fall, Michael J.
, p. 6897 - 6907 (2007/10/03)
The rhodium N-(arylsulfonyl)prolinate catalyzed decomposition of vinyldiazomethanes in the presence of alkenes leads to a very general method for the synthesis of functionalized cyclopropanes in a highly diastereoselective and enantioselective mode. A det
