ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNucleophilic α-Addition to Alkynoates. A Synthesis of Dehydroamino AcidsBarry M. Trost and Gregory R. DakeView Author Information Department Chemistry, Stanford University Stanford, California 94305 Cite this: J. Am. Chem. Soc. 1997, 119, 32, 7595–7596Publication Date (Web):August 13, 1997Publication History Received18 April 1997Published online13 August inissue 1...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTADDITION / CORRECTIONThis article has been corrected. View the notice.The First Stereoselective Total Synthesis of QuinineGilbert Stork, Deqiang Niu, A. Fujimoto, Emil R. Koft, James M. Balkovec, Tata, and Gregory DakeView Author Information Contribution from Department Chemistry, Columbia University, New York, York 10027 Cite this: J. Am. Chem. Soc. 2001, 123, 14, 3239–3242Publication Date (Web):March 17, 2001Publication History Received22...

Either silver trifluoromethanesulfonate or a mixture of gold(I) chloride, trifluoromethanesulfonate, and triphenylphosphine catalyze the formation pyrroles from substituted β-alkynyl ketones amines. The reactions proceed by using 5 mol % catalyst with yields isolated ranging 13% to 92%. Sixteen examples are used compare effectiveness each catalyst.

Alkaloids alchemy: A synthesis of the Lycopodium alkaloid (+)-fawcettidine (see structure) has been developed which requires 16 steps from (R)-(+)-pulegone as chiral starting material. Key include a platinum(II)-catalyzed annulation reaction functionalized enamide and one-pot Ramberg–Bäcklund process. Supporting information for this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z800522_s.pdf or author. Please note: The publisher not responsible content...

Polyamines are ubiquitous organic cations implicated in many physiological processes. Because they positively charged at pH, carrier-mediated systems necessary for effective membrane permeation, but the identity of specific polyamine transporter proteins eukaryotic cells remains unclear. Polyspecific cation transporters (OCTs) interact with natural and xenobiotic monovalent have been reported to transport dicationic compounds, including short putrescine. In this study, we used Xenopus...

[reaction: see text] Cyclic ene-N-p-toluenesulfonamides tethered to an electron-deficient alkyne undergo cycloisomerizations readily under the influence of catalytic Pt(II) salts (PtCl2 or [dppbPtmu-OH]2(BF4)2) AgOTf. Yields for this process range from 47% 99%. The resulting functionalized 2-azahydrindans can be reacted further using Diels-Alder reaction. Tandem cycloisomerization-cycloaddition reactions in one pot generate highly 1-azadecalin ring systems a stereocontrolled manner.

Cyclic enesulfonamides, enecarbamates, or enamides tethered to an alkyne cyclize readily with use of platinum(II) chloride. This reaction generates quaternary-substituted carbon centers within simple spiro-fused more complex tri- and tetracyclic heterocyclic ring systems. The yields for this process range from 50% 83%. [reaction: see text].

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNitrogen Pronucleophiles in the Phosphine-Catalyzed γ-Addition ReactionBarry M. Trost and Gregory R. DakeView Author Information Department of Chemistry, Stanford University, Stanford, California 94305-5080Cite this: J. Org. Chem. 1997, 62, 17, 5670–5671Publication Date (Web):August 22, 1997Publication History Received13 May 1997Published online22 August inissue 1...

The investigations of a synthetic route incorporating NBS-promoted semipinacol rearrangement to the 6-azaspiro[4.5]decane fragment within halichlorine (1) are presented. A convergent approach was pursued, utilizing two chiral, enantiomerically enriched building blocks, 2-trimethylstannyl piperidene 10 and substituted cyclobutanone 19. Noteworthy operations in this study include following: (a) highly diastereoselective reaction that established four stereogenic centers ketone 25 (b) use...

Enantioselective catalysis in moderate to excellent yields and ee's has been accomplished using a phosphaalkene-based ligand system. Specifically, the palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate chiral P(sp2),N(sp2) proceeds with variety malonate nucleophiles 73−95% yield (79−92% ee).

This Account describes the development of reactions catalyzed by platinum(II), silver(I), or gold(I) salts using substrates that feature enamides, enecarbamates, enesulfonamides as nucleophilic functional groups.

The key compound responsible for the aroma of bread, 6-acetyl-1,2,3,4-tetrahydropyridine (1), has been constructed in an efficient three-step procedure from 2-piperidone overall yield 56%. Compound 1 was liberated final step under basic conditions. A related synthetic route produced 2-acetyl-1-pyrroline (2), principal component cooked rice, 10% yield.

The reaction of E/Z-MesPC(Ph)(Py) (1, Mes = 2,4,6-Me3C6H2-) with (cod)PtCl2 or (cod)PdCl2 affords P,N-chelate complexes [MesPC(Ph)(Py)PtCl2] (2a) and [MesPC(Ph)(Py)PdCl2] (2b), respectively. Compounds 2a 2b were fully characterized spectroscopically, both by X-ray crystallography. molecular structures exhibited almost identical metrical parameters. PC bond lengths in [1.672(4) 1.675(3) Å, respectively] shortened substantially respect to that 1 [1.7043(16) Å]. Complex was explored as a...

Synthetic work toward the total synthesis of nitiol has culminated in construction two epimeric hydroxylated derivatives, 1,22-dihydroxynitianes. Key stereodefining steps A-ring fragment (13) were use a siloxy−epoxide rearrangement reaction, Pauson−Khand Norrish 1 photochemical cleavage and highly regio- stereoselective hydrostannylation reaction an ynoate. The stereochemistry synthetically challenging C-ring (20) was established using Ireland−Claisen Grubbs ring-closing metathesis process...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Synthetic Approach to the Fusicoccane A−B Ring Fragment Based on a Pauson−Khand Cycloaddition/Norrish Type 1 FragmentationGregory R. Dake*, Erik E. Fenster, and Brian O. Patrick†View Author Information Department of Chemistry, 2036 Main Mall, University British Columbia, Vancouver, B.C., Canada, V6T 1Z1[email protected]†Manager, Columbia X-Ray Analysis Facility.Cite this: J. Org. Chem. 2008, 73, 17, 6711–6715Publication Date (Web):July 25,...

Simply made and stable: An asymmetric phosphaalkene has been synthesized from L-valine, a readily available chiral precursor. This air-stable ligand forms P(sp2),N(sp2) complex to iridium(I) (see scheme) is the first example of new class phosphorus-based ligands which are expected possess excellent π-acceptor properties.

Cyclic enamine derivatives (enesulfonamides and enamides) tethered to an 1-arylalkynyl fragment undergo a platinum(II)-catalyzed tandem alkyne addition/Friedel-Crafts ring closure form nitrogen-containing polycyclic structures. Regioselectivity in the initial addition of enesulfonamide or enamide nucleophile platinum(II)-alkyne complex is important. Electron-rich arenes heterocycles led formation products resulting from 6-endo cyclization. Twenty-three examples this process are presented.

The total synthesis of cladoniamide G, a cytotoxic compound against MCF-7 breast cancer cells (10 μg/mL), was accomplished. Key steps in the sequence include oxidative dimerization 3-acetoxy-5-chloroindole and tandem process incorporating three steps: bimolecular carbonyl addition, lactam formation, carbamate removal.

Substituted tetrahydroxanthones are constructed using a DMAP-promoted tandem nucleophilic addition process. The reaction yields range from 39% to 73%. Disubstituted generated as ∼2.3:1 mixture of diastereomers favoring the formation trans-isomer.

The synthesis of enantiomerically pure pyridine-bridged phosphaalkene-oxazolines ArP═C(Ph)(2,6-C5H3NOx) (1, Ar = Mes/Mes*, Ox CNOCH(i-Pr)CH2/CNOCH(CH2Ph)CH2) is reported. This new ligand forms a κ(P), κ(2)(NN) dimeric complex with copper(I) (7) that dissociates into cationic κ(3)(PNN) monomeric upon addition neutral {[1a·CuL]OTf (8a-e): L PPh3 (a), P(OPh)3 (b), 2,6-lutidine (c), 4-DMAP (d), 1-methylimidazole (e)}. P-Cu bond lengths in 8 are influenced by the π-accepting/σ-donating properties...

[reaction: see text] Semipinacol-type rearrangements to produce azaspirocyclic ketones are presented. The yields and stereoselectivities of these reactions range from 67-94% yield 2.8:1 1:0 diastereoselectivity, respectively.

Azaspirocyclic ring systems are present in a variety of alkaloids. Functionalized 1-azaspirocyclopentanones (6, 7, 11, 12) can be efficiently constructed through semipinacol expansion reactions 2-(1-hydroxycyclobutyl)-p-toluenesulfonylenamides (4) promoted by either Bronsted acid ((S)-(+)-10-camphorsulfonic or HCl) N-bromosuccinimide, an electrophilic bromine source. Reactions N-bromosuccinimide tend to proceed higher yields (80-95%) and with greater diastereoselectivity (3:1-1:0) compared...

An asymmetric formal synthesis of fasicularin (1) is described. This natural product, isolated from the extracts marine invertebrate Nephteis fasicularis, has shown modest cytotoxicity towards Vero cells. Fasicularin among only two members cylindricine family products, along with lepadiformine (2), to possess a trans A-B ring junction. Key steps this approach 1 involve siloxy-epoxide semipinacol rearrangement 5 6, B-alkyl Suzuki-Miyaura coupling reaction by using enol...