-
[show abstract]
[hide abstract]
ABSTRACT: A Rh/Pd/Cu catalyst system led to an efficient synthesis of dihydroquinolinones in one-pot, two operations. The reaction features the first triple metal-catalyzed transformations in one reaction vessel, without any intermediate workup. The conjugate-addition/amidation/amidation reaction sequence is highly modular, divergent, and practical.
Organic Letters 04/2013; · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new enantioselective rhodium-catalyzed domino reaction is described that gives access to fused heterocycles by desymmetrization of alkyne-tethered cyclohexadienones. Two new C-C bonds and two stereocenters are formed in one step with good enantioselectivity. In contrast to prior reports, it was found that a vinylidene is not involved in the product formation but that syn-addition of the rhodium-aryl species onto the alkyne takes place.
Organic Letters 03/2013; 15(5):1148-51. · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A method for synthesizing chiral oxazolidinone scaffolds from readily available oxabicyclic alkenes is described. The reaction utilizes a domino sequence of Rh(I)-catalyzed asymmetric ring-opening (ARO) with sodium cyanate as a novel nucleophile followed by intramolecular cyclization to generate oxazolidinone products in excellent enantioselectivities (trans stereochemistry).
Organic Letters 02/2013; · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Done with 'F'lair: Enantioselective fluorination was achieved by Rh(I) -catalyzed ring opening of oxabicyclic alkenes using Et(3) N⋅3 HF. The chiral fluorinated scaffolds were obtained under mild reaction conditions in standard glass vessels, and served as useful building blocks for various chiral fluorinated targets. cod=cycloocta-1,5-diene, ppf=phenylphosphinoferrocene, THF=tetrahydrofuran.
Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A one-pot synthesis of the chiral dihydrobenzofuran framework is described. The method utilizes Rh-catalyzed asymmetric ring opening (ARO) and Pd-catalyzed C-O coupling to furnish the product in excellent enantioselectivity without isolation of intermediates. Systematic metal-ligand studies were carried out to investigate the compatibility of each catalytic system using product enantiopurity as an indicator.
Organic Letters 10/2012; · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Twisted molecules: A modular approach for the synthesis of tetrasubstituted helical alkenes by a palladium-catalyzed norbornene-mediated domino reaction is presented. This intermolecular domino process allows the formation of three CC bonds in one operation through a CH activation/carbopalladation/CH activation sequence.
Angewandte Chemie International Edition 08/2012; 51(39):9846-50. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A highly modular and stereoselective synthesis of tetrasubstituted helical alkenes is accomplished by a Pd-catalyzed norbornene-mediated domino reaction. This protocol features the rapid assembly of four C-C bonds via sequential C-H activations and carbopalladations along with efficient access to enantiopure bromoalkyl aryl alkyne precursors using homologative alkynylation as the key transformation. Three distinct elements of stereoselectivity were observed in the preparation of the chiral helical alkenes: retention of stereochemistry of the substrates, induced helical diastereoselectivity in the alkene formation, and the exclusive exo-facial selectivity of the norbornene incorporation.
Organic Letters 06/2012; · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Water-induced asymmetric ring opening: Enantio-enriched 2-hydroxy-1-tetralones are formed from oxabicyclic alkenes through a novel Rh(I) -catalyzed domino reaction. The proposed mechanism involves water-induced asymmetric ring opening to generate chiral trans-1,2-diol intermediates and subsequent enantioselective isomerization.
Angewandte Chemie International Edition 04/2012; 51(22):5400-4. · 13.45 Impact Factor
-
Organic Syntheses 01/2012; 89:230-242.
-
[show abstract]
[hide abstract]
ABSTRACT: A convenient approach toward polycyclic frameworks containing fused 1,2,3-triazoles is described. The synthesis consists of a Cu-catalyzed cycloaddition and an intramolecular Pd-catalyzed direct arylation or Heck reaction, and affords the products in good to excellent yields.
Chemical Communications 11/2011; 48(1):55-7. · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An efficient and versatile synthesis of chiral tetralins has been developed using both inter- and intramolecular Friedel-Crafts alkylation as a key step. The readily available hydronaphthalene substrates were prepared via a highly enantioselective metal-catalyzed ring opening of meso-oxabicyclic alkenes followed by hydrogenation. A wide variety of complex tetracyclic compounds have been isolated with high levels of regio-, diastereo-, and enantioselectivity.
The Journal of Organic Chemistry 09/2011; 76(21):9031-45. · 4.45 Impact Factor
-
Angewandte Chemie International Edition 09/2011; 50(39):9089-92. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A regio- and stereoselective rhodium-catalyzed synthesis of trisubstituted allylic alcohols is described. The utility of these synthons is demonstrated in a convenient synthesis of indenes and quinolines.
Organic Letters 09/2011; 13(19):5314-7. · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Aryl bromides have been used to prepare a variety of nitrogen- and oxygen-containing heterocycles featuring new carbon-carbon and carbon-iodine bonds. This palladium-catalyzed carbohalogenation requires potassium iodide for the reaction to proceed in high yields. Additionally, the first examples of domino carbohalogenation reactions have been demonstrated using both aryl iodide and aryl bromide starting materials. Complex products with multiple rings and stereogenic centers are generated in excellent yields with moderate to excellent diastereoselectivities.
Journal of the American Chemical Society 09/2011; 133(38):14916-9. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A short and highly modular three-step synthesis of a new class of substituted naphthothiophenes has been developed exploiting a Pd-catalyzed tandem direct arylation/Suzuki coupling transformation as the key step.
Organic Letters 08/2011; 13(16):4236-9. · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Although the chemistry of arynes is well developed, some challenges still remain. The ene reaction of arynes has not gained widespread use in synthesis as a result of poor yields and selectivity. A general, high yielding and selective intramolecular aryne-ene reaction is described providing various benzofused carbo- and heterocycles. Mechanistic data is presented, and a rationale for the resulting stereochemistry is discussed.
Journal of the American Chemical Society 08/2011; 133(36):14200-3. · 9.91 Impact Factor
-
Angewandte Chemie International Edition 06/2011; 50(32):7346-9. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An efficient and versatile synthesis of cis-hexahydrobenzophenanthridines starting from readily available tetralins has been developed using an intramolecular Friedel-Crafts alkylation as a key step. The substrates were prepared via a highly stereocontrolled rhodium-catalyzed ring-opening reaction of meso-oxabicyclic alkenes and a hydrogenation sequence. Thus, a wide variety of complex tetracyclic compounds have been isolated with a high level of regio-, diastereo-, and enantioselectivity.
Organic Letters 06/2011; 13(12):3000-3. · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Mechanistic studies of a palladium-catalyzed regioselective aryl C-H functionalization of 2-pyrrole phenyl iodide with norbornene are presented. Kinetic and spectroscopic analyses together with crystallographic data provide evidence for intermediates in a proposed stepwise mechanism. On the basis of the mechanistic studies, the origin of the regioselectivity is due to a ligand exchange between I(-) and HO(-) on the norbornyl palladium complex. These mechanistic studies also implicate that either alkoxide or water is responsible for the formation of the palladacycle, but a reversible ring-opening-ring-closing process of the palladacycle with HX can retard the rate of reaction of a key intermediate. The significant aspects of the proposed mechanism are discussed in detail.
Chemistry 06/2011; 17(29):8175-88. · 5.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The use of aryl triflates as reaction partners in a palladium-catalyzed domino direct arylation/N-arylation provides a great advantage due to the availability of starting materials. Furthermore, it allows expedient access to biologically interesting benzo[c]phenanthridine alkaloids.
Organic Letters 02/2011; 13(6):1486-9. · 5.86 Impact Factor
