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John A. Porco - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of a novel chemotype via sequential metal-catalyzed Cycloisomerizations.
Beilstein Journal of Organic Chemistry, 2012Co-Authors: Bo Leng, Stephanie Chichetti, Aaron B. Beeler, John A. PorcoAbstract:Sequential Cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I)-mediated Cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II)-catalyzed enyne Cycloisomerization.
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synthesis of pyrrolo isoquinolines related to the lamellarins using silver catalyzed Cycloisomerization dipolar cycloaddition
Journal of the American Chemical Society, 2007Co-Authors: John A. PorcoAbstract:Synthesis of pyrrolo-isoquinolines related to the lamellarin alkaloids employing silver-catalyzed Cycloisomerization−dipolar cycloaddition of alkynyl N-benzylidene glycinates is described. Mechanistic studies revealed Ag(I)-catalyzed Cycloisomerization to an azomethine ylide as a key step for formation of angular pyrrolo-isoquinolines.
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Synthesis of Pyrrolo-isoquinolines Related to the Lamellarins Using Silver-Catalyzed Cycloisomerization/Dipolar Cycloaddition
Journal of the American Chemical Society, 2007Co-Authors: John A. PorcoAbstract:Synthesis of pyrrolo-isoquinolines related to the lamellarin alkaloids employing silver-catalyzed Cycloisomerization−dipolar cycloaddition of alkynyl N-benzylidene glycinates is described. Mechanistic studies revealed Ag(I)-catalyzed Cycloisomerization to an azomethine ylide as a key step for formation of angular pyrrolo-isoquinolines.
Barry M. Trost - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Chiral, Densely Substituted Pyrrolidones via Phosphine-Catalyzed Cycloisomerization
Organic Letters, 2019Co-Authors: Barry M. Trost, Elumalai Gnanamani, Chao-i Joey Hung, Christopher A. KalnmalsAbstract:Densely substituted chiral pyrrolidones are synthesized via phosphine-catalyzed Cycloisomerization of enantioenriched β-amino ynones, which are prepared in a single step using a highly enantioselective Zn-ProPhenol-catalyzed Mannich reaction. The exocyclic alkenes in the cyclization products provide versatile handles for further transformations and typically form with good E/ Z selectivity. This Cycloisomerization method can be performed in streamlined fashion, without purification of the intermediate Mannich adduct, and extends to anthranilic acid based scaffolds in addition to ProPhenol-derived Mannich adducts.
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Synthesis of Chiral, Densely Substituted Pyrrolidones via Phosphine-Catalyzed Cycloisomerization
2019Co-Authors: Barry M. Trost, Elumalai Gnanamani, Chao-i Joey Hung, Christopher A. KalnmalsAbstract:Densely substituted chiral pyrrolidones are synthesized via phosphine-catalyzed Cycloisomerization of enantioenriched β-amino ynones, which are prepared in a single step using a highly enantioselective Zn-ProPhenol-catalyzed Mannich reaction. The exocyclic alkenes in the cyclization products provide versatile handles for further transformations and typically form with good E/Z selectivity. This Cycloisomerization method can be performed in streamlined fashion, without purification of the intermediate Mannich adduct, and extends to anthranilic acid based scaffolds in addition to ProPhenol-derived Mannich adducts
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Ruthenium- and palladium-catalyzed enyne Cycloisomerizations: differentially stereoselective syntheses of bicyclic structures.
Journal of the American Chemical Society, 2008Co-Authors: Barry M. Trost, Eric M. Ferreira, Alicia C. GutierrezAbstract:Enyne Cycloisomerizations can provide an efficient means for forming carbon−carbon bonds. We describe stereoselectively dichotomous enyne Cycloisomerizations, entirely dependent on the selection of catalytic manifold. Ruthenium catalysis provides trans-fused bicyclic systems, whereas palladium catalysis provides the analogous cis-fused bicycles. A number of substrates are investigated, and the outcomes ultimately offer a clear mechanistic rationale for these observations.
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Exploiting the Pd- and Ru-Catalyzed Cycloisomerizations: Enantioselective Total Synthesis of (+)-Allocyathin B2
Journal of the American Chemical Society, 2005Co-Authors: Barry M. Trost, Li Dong, Gretchen M. SchroederAbstract:Pd- and Ru-catalyzed Cycloisomerizations of 1,6-enynes are compared and contrasted. Such considerations led to the enantioselective synthesis of a cyathin terpenoid, (+)-allocyathin B2 (1). The synthesis features a Pd-catalyzed asymmetric allylic alkylation (AAA) to install the initial quaternary center, a Ru-catalyzed diastereoselective Cycloisomerization to construct the six-membered ring, and a diastereoselective hydroxylative Knoevenagel reaction to introduce the final hydroxyl group. We demonstrate for the first time a mechanism-based stereochemical divergence in Pd- and Ru-catalyzed Cycloisomerization reactions as well as in creation of alkene geometry with alkynes bearing a carboalkoxy group. Mechanistic rationalization is proposed for these observations.
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Ruthenium-Catalyzed Cycloisomerizations of Diynols
Journal of the American Chemical Society, 2005Co-Authors: Barry M. Trost, Michael T. RuddAbstract:A wide variety of diynols containing tertiary, secondary, and primary propargylic alcohols undergo a Cycloisomerization reaction to form dienones and dienals in the presence of a catalytic amount of [CpRu(CH3CN)3]PF6. The formation of five- and six-membered rings is possible using this methodology. Secondary diynols react to form single geometrical isomeric dienones and -als. Primary diynols undergo a Cycloisomerization as well as a hydrative cyclization process. The utility of primary diynol Cycloisomerization is demonstrated in a synthesis of (+)-α-kainic acid.
Min Shi - One of the best experts on this subject based on the ideXlab platform.
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Recent Advances in the Cycloisomerizations of Methylenecyclopropanes using Gold Catalysis.
Chemistry - A European Journal, 2018Co-Authors: Wei Fang, Min ShiAbstract:During the past decades, Cycloisomerizations of methylenecyclopropanes using gold catalysis have attracted much attention from organic chemists. The different patterns of gold(I)-catalyzed Cycloisomerizations of methylenecyclopropanes have been developed, and they can be classified as ring-opening and ring-expansion reaction patterns. This synthetic methodology provides a new approach to novel cyclic- or polycyclic compounds. The corresponding products have great potential for material science, medicinal chemistry and total synthesis. This Concept article will mainly focus on the recent advances in the Cycloisomerizations of methylenecyclopropanes in the past four years.
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Cu(I)-Catalyzed Coupling and Cycloisomerization of Diazo Compounds with Terminal Yne-Alkylidenecyclopropanes: Synthesis of Functionalized Cyclopenta[b]naphthalene Derivatives
2018Co-Authors: Xiao-yu Zhang, Min ShiAbstract:A Cu(I)-catalyzed coupling and Cycloisomerization of diazo compounds with terminal yne-alkylidenecyclopropanes (ACPs) has been presented. This reaction starts from the formation of an allenic intermediate in the Cu(I)-catalyzed cross-coupling reaction of a diazo compound with terminal alkyne in yne-tethered ACP and then undergoes a domino Cycloisomerization of a 6π-electrocyclization and cyclopropane ring-opening rearrangement to give functionalized cyclopenta[b]naphthalene derivatives in moderate to excellent yields under mild conditions
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Gold(I)-Catalyzed Cycloisomerization of ortho-(Propargyloxy)arenemethylenecyclopropanes Controlled by Adjacent Substituents at Aromatic Rings.
Chemistry - A European Journal, 2017Co-Authors: Wei Fang, Yin Wei, Xiang‐ying Tang, Min ShiAbstract:Gold(I)-catalyzed Cycloisomerization of ortho-(propargyloxy)arenemethylenecyclopropanes afforded two different types of products, that is, products of methylenecyclopropane migration and Cycloisomerization products of the methylenecyclopropane moiety, controlled jointly by electronic and steric effects of the adjacent substituents. Furthermore, the corresponding Cycloisomerization products could be also produced in an enantiomerically enriched manner.
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Gold(I)-Catalyzed Intramolecular Cycloisomerization of Propargylic Esters with Furan Rings.
ChemInform, 2015Co-Authors: Jin‐ming Yang, Xiang‐ying Tang, Min ShiAbstract:The intramolecular Cycloisomerization of a diverse range of substrates using Au(I)-catalysis is presented.
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gold catalyzed Cycloisomerization of yne vinylidenecyclopropanes a three carbon synthon for 3 2 cycloadditions
ChemInform, 2014Co-Authors: Wei Yuan, Yin Wei, Min Shi, Xiangying TangAbstract:A novel Cycloisomerization/rearrangement of newly synthesized yne-vinylidenecyclopropanes (I) and (III) catalyzed by a sterically hindered gold catalyst is reported.
Frank E. Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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Sequential exo-mode oxacyclizations for the synthesis of the CD substructure of brevenal
The Journal of Antibiotics, 2019Co-Authors: Noah A. Setterholm, Frank E. McdonaldAbstract:We describe a novel strategy for synthesizing the CD bicyclic ether substructure of the fused polycyclic ether natural product brevenal. This product arises from a three-step sequence beginning with (1) regio- and diastereoselective iodoetherification of an acyclic diene-diol, followed by (2) alkene metathesis with an epoxyalkene synthon, concluding with (3) palladium-catalyzed Cycloisomerization. Despite the modest yield and long reaction period for the Cycloisomerization step, these studies provide valuable insights into the nature of byproducts generated and the mechanisms by which they form. This work demonstrates a portion of a larger synthetic strategy for constructing the pentacyclic core of brevenal from an acyclic precursor.
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fischer carbene catalysis of alkynol Cycloisomerization application to the synthesis of the altromycin b disaccharide
Organic Letters, 2007Co-Authors: Onsuk Koo, Frank E. McdonaldAbstract:The tungsten-catalyzed Cycloisomerization of alkynyl alcohols can be conducted without using photochemistry, using a stable tungsten Fischer carbene as the precatalyst for this transformation. A variety of alkynyl alcohols undergo Cycloisomerization under these conditions to provide endocyclic enol ethers of five-, six-, and seven-membered ring sizes. The utility of this method is further demonstrated in the stereoselective synthesis of the disaccharide substructure of altromycin B.
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Density Functional Study of Mo-Carbonyl-Catalyzed Alkynol Cycloisomerization: Comparison with W-Catalyzed Reaction.
Organometallics, 2005Co-Authors: Taraneh Nowroozi-isfahani, Frank E. Mcdonald, Djamaladdin G. Musaev, Keiji MorokumaAbstract:Mo-catalyzed endo-Cycloisomerizations of alkynes tethered to alcohols have been studied using density functional theory, and comparisons were made with the W-catalyzed reaction. The Cycloisomerization is initiated with the formation of metal alkyne pi complex and is followed by the rate-determining step, which transforms the pi complex to a vinylidene carbene complex, considered to be critical for endo-mode cyclization. Several different alkynols have been selected to investigate five- and six-membered ring endo-Cycloisomerizations in the presence of Mo(CO)(5) catalyst. The energy barriers calculated for five- and six-membered ring Cycloisomerizations are within a range of 25-30 kcal/mol for most cases studied, showing no significant energy difference between the two metals. The stabilization effect of THF and Et(3)N solvents and the substitution reaction of THF by alkynol substrates in the reaction process with Mo and W complexes are studied as well. The principal difference between Mo- and W-catalyzed Cycloisomerization processes appears to be the initial formation of a pi complex, which is more stabilizing for formation of the W-alkyne vs Mo-alkyne complexes.
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Stereoselective Synthesis of d-Desosamine and Related Glycals via Tungsten-Catalyzed Alkynol Cycloisomerization
Organic Letters, 2004Co-Authors: Mary H. Davidson, Frank E. McdonaldAbstract:Stereoselective synthesis of d-desosamine diacetate ester (iii, R = Ac) was achieved from the glycal (ii) generated by tungsten carbonyl-catalyzed Cycloisomerization of the corresponding amino-alkynol (i). A wide variety of N-substituents (R, R‘) are compatible with the Cycloisomerization, provided that at least one R or R‘ is an acyl derivative.
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Computational studies of tungsten-catalyzed endo-selective Cycloisomerization of 4-pentyn-1-ol.
Journal of the American Chemical Society, 2002Co-Authors: Yinghong Sheng, Frank E. Mcdonald, Djamaladdin G. Musaev, K. Subba Reddy, Keiji MorokumaAbstract:Endo- and exo-Cycloisomerizations of 4-pentyn-1-ol have been studied computationally with density functional theory, in conjunction with double-ζ and triple-ζ basis sets, both in the absence and in the presence of tungsten carbonyl catalyst. In the absence of the catalyst, both endo- and exo-Cycloisomerizations have been calculated to have a very high activation barrier of ∼50−55 kcal/mol and cannot take place. With tungsten pentacarbonyl catalyst, endo-Cycloisomerization becomes a complex multiple-step reaction and proceeds with a rate-determining barrier of 26 kcal/mol at the Cα → Cβ hydride migration step to form a vinylidene intermediate. The primary role of the tungsten catalyst is to stabilize the vinylidene intermediate, thus lowering the rate-determining barrier. The second important role of the tungsten catalyst in endo-Cycloisomerization is to assist the OH hydride migration to Cα by making it a multistep process with small activation barriers. The exo-Cycloisomerization with the catalyst still ...
Ken Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Rhodium-Catalyzed Cycloisomerization of 2-Silylethynyl Phenols and Anilines via 1,2-Silicon Migration
Organic Letters, 2016Co-Authors: Hiroshi Kanno, Keiichi Noguchi, Yu Shibata, Kyosuke Nakamura, Ken TanakaAbstract:It has been established that a cationic rhodium(I)/BINAP complex catalyzes the Cycloisomerization of 2-silylethynylphenols, leading to 3-silylbenzofurans, via 1,2-silicon migration. Similarly, the Cycloisomerization of 2-silylethynylanilines, leading to 3-silylindoles, via 1,2-silicon migration was catalyzed by a cationic rhodium(I)/H8–BINAP complex.
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enantioselective Cycloisomerization of 1 6 enynes to bicyclo 3 1 0 hexanes catalyzed by rhodium and benzoic acid
Journal of the American Chemical Society, 2014Co-Authors: Koji Masutomi, Keiichi Noguchi, Ken TanakaAbstract:It has been established that a cationic Rh(I)/(S)-Segphos or (S)-DTBM-Segphos complex and benzoic acid catalyze the enantioselective Cycloisomerization of 1,6-enynes, possessing carbonyl groups at the enyne linkage, to 2-alkylidenebicyclo[3.1.0]hexanes. The present Cycloisomerization may involve site selective γ-hydrogen elimination. The one-pot enantioselective Cycloisomerization and lactonization of 1,6-enynes, leading to bicyclic lactones, has also been accomplished.
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Highly enantioselective construction of axial chirality by palladium-catalyzed Cycloisomerization of N-alkenyl arylethynylamides.
Organic Letters, 2009Co-Authors: Hidetomo Imase, Masao Hirano, Takeshi Suda, Yu Shibata, Keiichi Noguchi, Ken TanakaAbstract:A cationic palladium(II)/(S)-xyl-Segphos complex catalyzes enantioselective Cycloisomerizations of N-alkenyl arylethynylamides leading to axially chiral 4-aryl-2-pyridones in high yields with high ee values. The present catalysis represents the first enantioselective construction of axial chirality by the transition-metal-catalyzed Cycloisomerization.
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cationic rhodium i segphos catalyzed Cycloisomerization of 1 6 and 1 7 diynes in the presence of 1 2 cyclohexanedione
Organic Letters, 2007Co-Authors: Ken Tanaka, Yousuke Otake, Masao HiranoAbstract:We have developed the first catalytic Cycloisomerization of 1,6- and 1,7-diynes leading to trienes and vinylpyrroles by using a cationic rhodium(I)/Segphos complex (2.5−10 mol %) and 1,2-cyclohexanedione (100 mol %). 1,2-Cyclohexanedione may effectively occupy vacant coordination sites and thus promote the present Cycloisomerization.
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Cationic rhodium(I)/segphos-catalyzed Cycloisomerization of 1,6- and 1,7-diynes in the presence of 1,2-cyclohexanedione.
Organic Letters, 2007Co-Authors: Ken Tanaka, Yousuke Otake, Masao HiranoAbstract:We have developed the first catalytic Cycloisomerization of 1,6- and 1,7-diynes leading to trienes and vinylpyrroles by using a cationic rhodium(I)/Segphos complex (2.5−10 mol %) and 1,2-cyclohexanedione (100 mol %). 1,2-Cyclohexanedione may effectively occupy vacant coordination sites and thus promote the present Cycloisomerization.
