- Stereodivergent Total Syntheses of (+)-Monomorine I and (+)-Indolizidine 195B
-
A simple and efficient stereoselective total syntheses of two natural products (+)-monomorine I and (+)-indolizidine 195B in high yields starting from a readily available alcohol is described. The key step in this synthetic route exploits the judicious use of solvent to enable a closed or open transition state in a nucleophilic addition of Grignard reagent to sulfinimine, giving selective access to two distinct diastereomers required for the formation of the two target natural products.
- Dawood, Rafid S.,Stockman, Robert A.
-
-
Read Online
- A Supramolecular Strategy for Selective Catalytic Hydrogenation Independent of Remote Chain Length
-
Performing selective transformations on complex substrates remains a challenge in synthetic chemistry. These difficulties often arise due to cross-reactivity, particularly in the presence of similar functional groups at multiple sites. Therefore, there is a premium on the ability to perform selective activation of these functional groups. We report here a supramolecular strategy where encapsulation of a hydrogenation catalyst enables selective olefin hydrogenation, even in the presence of multiple sites of unsaturation. While the reaction requires at least one sterically nondemanding alkene substituent, the rate of hydrogenation is not sensitive to the distance between the alkene and the functional group, including a carboxylate, on the other substituent. This observation indicates that only the double bond has to be encapsulated to effect hydrogenation. Going further, we demonstrate that this supramolecular strategy can overcome the inherent allylic alcohol selectivity of the free catalyst, achieving supramolecular catalyst-directed regioselectivity as opposed to directing-group selectivity.
- Bender, Trandon A.,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
-
supporting information
p. 11806 - 11810
(2019/08/22)
-
- Photocatalytic One-Pot Synthesis of Homoallyl Ketones via a Norrish Type i Reaction of Cyclopentanones
-
A photocatalytic synthesis of homoallyl ketones was achieved via a one-pot procedure starting from a Norrish Type I reaction of cyclopentanones, followed by a decatungstate-catalyzed hydroacylation of electron-deficient olefins by the resulting 4-pentenals. The site-selective formyl H-abstraction in the second step can be explained by radical polar effects in the transition state.
- Okada, Megumi,Yamada, Keiichi,Fukuyama, Takahide,Ravelli, Davide,Fagnoni, Maurizio,Ryu, Ilhyong
-
p. 9365 - 9369
(2015/09/28)
-
- Ligand-controlled, tunable silver-catalyzed C-H amination
-
The development of readily tunable and regioselective C-H functionalization reactions that operate solely through catalyst control remains a challenge in modern organic synthesis. Herein, we report that simple silver catalysts supported by common nitrogenated ligands can be used to tune a nitrene transfer reaction between two different types of C-H bonds. The results reported herein represent the first example of ligand-controlled and site-selective silver-promoted C-H amination.
- Alderson, Juliet M.,Phelps, Alicia M.,Scamp, Ryan J.,Dolan, Nicholas S.,Schomaker, Jennifer M.
-
supporting information
p. 16720 - 16723
(2015/01/16)
-
- Stereoselective synthesis of cis-2,5-disubstituted pyrrolidines via Wacker-type aerobic oxidative cyclization of alkenes with tert-butanesulfinamide nucleophiles
-
Palladium(II)-catalyzed aerobic oxidative cyclization of alkenes with tethered tert-butanesulfinamides furnishes enantiopure 2,5-disubstituted pyrrolidines, originating from readily available and easily diversified starting materials. These reactions are the first reported examples of metal-catalyzed addition of sulfinamide nucleophiles to alkenes.
- Redford, Joanne E.,McDonald, Richard I.,Rigsby, Matthew L.,Wiensch, Joshua D.,Stahl, Shannon S.
-
supporting information; experimental part
p. 1242 - 1245
(2012/05/20)
-
- Iron-catalyzed intramolecular allylic C-H amination
-
A highly selective C-H amination reaction under iron catalysis has been developed. This novel system, which employs an inexpensive, nontoxic [Fe IIIPc] catalyst (typically used as an industrial ink additive), displays a strong preference for allylic C-H amination over aziridination and all other C-H bond types (i.e., allylic > benzylic > ethereal > 3° > 2° ? 1°). Moreover, in polyolefinic substrates, the site selectivity can be controlled by the electronic and steric character of the allylic C-H bond. Although this reaction is shown to proceed via a stepwise mechanism, the stereoretentive nature of C-H amination for 3° aliphatic C-H bonds suggests a very rapid radical rebound step.
- Paradine, Shauna M.,White, M. Christina
-
supporting information; scheme or table
p. 2036 - 2039
(2012/03/11)
-
- Hydrazides as tunable reagents for alkene hydroamination and aminocarbonylation
-
(Chemical Equation Presented) Benzoic hydrazides (R = Ph), which are remarkably bench and thermally stable reagents (often up to 230°C), afford intramolecular hydroamination products upon heating at high temperatures (120-235°C). A concerted Cope-type hydroamination event, followed by a hydrazide-mediated proton transfer step of the hydrazinium ylide intermediate, is proposed and supported by DFT calculations. In contrast, a simple modification of the reagent structure (R = Ot-Bu or NH2) favors the formation of aminocarbonylation products at 200°C, and the latter reaction is shown to be stereospecific. Copyright
- Roveda, Jean-Gregoire,Clavette, Christian,Hunt, Ashley D.,Gorelsky, Serge I.,Whipp, Christopher J.,Beauchemin, Andre M.
-
supporting information; experimental part
p. 8740 - 8741
(2009/12/04)
-
- Total synthesis of ent-lepadin F and G by a tandem ene-yne-ene ring closing metathesis
-
(Chemical Equation Presented) The first total synthesis of the decahydroquinoline-alkaloids lepadin F and G is described. As key steps, the decahydroquinoline skeleton has been synthesized by utilizing a tandem ene-yne-ene ring closing metathesis of an acyclic precursor followed by a stereoselective hydrogenation of the resulting diene moiety. The selectivity of these two steps was achieved by a well-directed hydroxyl protection strategy. The synthesized compounds were found to be enantiomers of natural lepadin F and G, consequently the absolute configuration of the natural compounds could be assigned.
- Niethe, Alexander,Fischer, Dirk,Blechert, Siegfried
-
p. 3088 - 3093
(2008/09/19)
-
- Tandem inter [4+2]/intra [3+2] cycloadditions. 8. Cycloadditions with unactivated dipolarophiles
-
The tandem intermolecular [4+2]/intramolecular [3+2] cycloaddition of nitroalkenes bearing a pendant olefin is presented. The success of the tandem process is remarkable in view of the potential for intramolecular reaction with the tethered alkene. Cycloadditions of di- and trisubstituted nitroalkenes bearing two- and three-methylene tethers which contain mono-, di- and trisubstituted olefins are described. In all cases the tandem process is high yielding (with n-butyl vinyl ether as the dienophile) and highly stereoselective. Hydrogenolysis of the resulting nitroso acetals leads cleanly to fused pyrrolidines in high yields.
- Denmark, Scott E.,Senanayake
-
p. 11579 - 11600
(2007/10/03)
-
- Seven-Membered Ring Synthesis Based On Arene Olefin Cycloadditions: The Total Synthesis of (+/-)-Rudmollin
-
The total synthesis of the antileukemic agent rudmollin (1) is described, based on a new approach to complex seven-membered ring synthesis involving the arene olefin meta photocycloaddition.
- Wender, Paul A.,Fisher, Karl
-
p. 1857 - 1860
(2007/10/02)
-