ABSTRACT
A highly enantioselective one-pot synthesis of cyclopropane-fused tetrahydroquinolines bearing carbonyl functionalities, which are difficult to synthesize using conventional methods, is reported. Employing readily accessible alkene-tethered anthranilaldehydes, hydrazone formation and subsequent Ru-catalyzed intramolecular cyclopropanation furnish the desired products in ≤87% yield and ≤95% ee under mild conditions. Various anthranilaldehydes, functionalized alkenes, and N-aryl sulfonyl groups are tolerated, and a series of synthetic transformations were conducted to demonstrate the practical utility.
ABSTRACT
The synthesis and optical resolution of helically chiral 5,6,9,10-tetrahydro-1-[6]helicenethiol and its subsequent transformations to enantiopure 1-sulfur-functionalized [6]helicenes are reported. A novel enantiopure [7]thiahelicene having a thiophene ring at the terminal position of the [6]helicene skeleton was synthesized.
ABSTRACT
An efficient and enantioselective synthesis of oxa[9]helicenes has been established via vanadium(V)-catalyzed oxidative coupling/intramolecular cyclization of polycyclic phenols. A newly developed vanadium complex cooperatively functions as both a redox and Lewis acid catalyst to promote the present sequential reaction and afford oxa[9]helicenes in good yields with up to 94% ee.
ABSTRACT
An enantioselective synthesis of tetrahydropyrrolo[1,2-c]pyrimidine-1,3-diones via a palladium-catalyzed intramolecular oxidative aminocarbonylation is described. The carbon-carbon double bond of alkenylurea substrates has been shown to react intramolecularly with a nitrogen nucleophile in the presence of a palladium catalyst under a carbon monoxide atmosphere. The use of a chiral spiro bis(isoxazoline) ligand (SPRIX) is essential to obtain the desired products in optically active forms. In comparison with the coordination ability of other known ligands, this peculiar character of SPRIX originates from two structural characteristics: low sigma-donor ability of the isoxazoline coordination site and rigidity of the spiro skeleton.
Subject(s)
Alkenes/chemistry , Isoxazoles/chemistry , Organometallic Compounds/chemistry , Palladium/chemistry , Spiro Compounds/chemistry , Urea/analogs & derivatives , Urea/chemistry , Amination , Catalysis , Ligands , Models, Chemical , Oxidation-Reduction , Pyrimidines/chemical synthesis , Pyrimidines/chemistry , Pyrroles/chemical synthesis , Pyrroles/chemistry , StereoisomerismABSTRACT
The first asymmetric Pd(II)/Pd(IV) catalysis has been achieved by employing the combination of a hypervalent iodine reagent and a chiral ligand, SPRIX. Enantioselective cyclization of enyne derivatives catalyzed by the Pd-i-Pr-SPRIX complex furnished lactones bearing a bicyclo[3.1.0]hexane skeleton with up to 95% ee.