Metal-Mediated Carbocyclic Construction: The Chen Synthesis of Ageliferin

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Pd Catalyst ◽  
Stanford University ◽  
Terminal Alkyne ◽  
Max Planck ◽  
Enantioselective Oxidation ◽  
Emory University ◽  
Peking University ◽  
Rh Catalyst ◽  
Oseltamivir Phosphate

Djamaladdin G. Musaev and Huw M.L. Davies of Emory University designed (J. Am. Chem. Soc. 2011, 133, 19198) a Rh catalyst that added 2 to 1 to give 3 with high dr and ee. Shunichi Hashimoto of Hokkaido University reported (Angew. Chem. Int. Ed. 2011, 50, 6803) a Rh catalyst that would add the α-diazo ester 5 to a terminal alkyne 4 to give the cyclopropene 6 in high ee. Gaëlle Blond and Jean Suffert of the Université de Strasbourg cyclized (Adv. Synth. Catal. 2011, 353, 3151) the alkyne 7, then coupled the Pd intermediate with a terminal alkyne 8 to give the cyclobutane 9. Nuno Maulide of the Max-Planck-Institute Mülheim ionized (Angew. Chem. Int. Ed. 2011, 50, 12631) the lactone 10 to a prochiral intermediate, which could then be coupled with 11 to give either diastereomer of 12 in high ee. Martin Hiersemann of the Technische Universität Dortmund devised (Org. Lett. 2011, 13, 4438) a Pd catalyst for the selective cyclization of 13 to 14. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry, Tokyo effected (Angew. Chem. Int. Ed. 2011, 50, 7616) the enantioselective Conia ene cyclization of 15 to 16. Barry M. Trost of Stanford University developed (J. Am. Chem. Soc. 2011, 133, 19483) an enantioselective variant of the trimethylenemethane cycloaddition of 18 to 17 to give 19. In the course of a synthesis of (–)-oseltamivir phosphate, Masahiko Hayashi of Kobe University found (J. Org. Chem. 2011, 76, 5477) conditions for the enantioselective oxidation of 20 to 21. Quanrui Wang of Fudan University and Andreas Goeke of Givaudan Fragrances (Shanghai) cyclized (J. Org. Chem. 2011, 76, 5825) the propargylic acetate 22 to the cyclohexenone 23. Chuang-chuang Li, Tuoping Luo, and Zhen Yang of Peking University cyclized (J. Am. Chem. Soc. 2011, 133, 14944) the diyne 24 to the lactone 25. Hiromitsu Takayama of Chiba University used (Angew. Chem. Int. Ed. 2011, 50, 8025) the silyl tether of 26 to constrain the diastereomeric outcome of the cyclization to 27.

Transition Metal Catalyzed Construction of Carbocyclic Rings: (-)-Hamigeran B

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Allylic Oxidation ◽  
Cyclic Enones ◽  
Peking University ◽  
Cu Catalyst ◽  
Rh Catalyst ◽  
Queen's University ◽  
Carbocyclic Rings ◽  
Metal Catalyzed ◽  
The University ◽  
Cyclic Alkenes

Several elegant methods for the enantioselective transformation of preformed prochiral rings have been put forward. Derek R. Boyd of Queen’s University, Belfast devised (Chem. Commun. 2008, 5535) a Cu catalyst that effected allylic oxidation of cyclic alkenes such as 1 with high ee. Christoph Jaekel of the Ruprecht-Karls-Universität Heidelberg established (Adv. Synth. Cat. 2008, 350, 2708) conditions for the enantioselective hydrogenation of cyclic enones such as 3. Marc L. Snapper of Boston College developed (Angew. Chem. Int. Ed. 2008, 47, 5049) a Cu catalyst for the enantioselective allylation of activated cyclic enones such as 5. Alexandre Alexakis of the University of Geneva showed (Angew. Chem. Int. Ed. 2008, 47, 9122) that dienones such as 8 could be induced to undergo 1,4 addition, again with high ee. Tsutomu Katsuki of Kyushu University originated (J. Am. Chem. Soc. 2008, 130, 10327) an Ir catalyst for the addition of diazoacetate 11 to alkenes such as 10 to give the cyclopropane 12 with high chemo-, enantio- and diastereoselectivity. Weiping Tang of the University of Wisconsin found (Angew. Chem. Int. Ed. 2008, 47, 8933) a silver catalyst that rearranged cyclopropyl diazo esters such as 13 to the cyclobutene 14 with high regioselectivity. Zhang-Jie Shi of Peking University demonstrated (J. Am. Chem. Soc. 2008, 130, 12901) that under oxidizing conditions, a Pd catalyst could cyclize 15 to 16. Sergio Castillón of the Universitat Rovira i Virgili, Tarragona devised (Organic Lett. 2008, 10, 4735) a Rh catalyst for the enantioselective cyclization of 17 to 18. Virginie Ratovelomanana-Vidal of the ENSCP Paris and Nakcheol Jeong of Korea University established (Adv. Synth. Cat. 2008, 350, 2695) conditions for the enantioselective intramolecular Pauson-Khand cyclization of 19 to give, after hydrolysis, the cyclopentenone 20. Quanrui Wang of Fudan University, Several elegant methods for the enantioselective transformation of preformed prochiral rings have been put forward. Derek R. Boyd of Queen’s University, Belfast devised (Chem. Commun. 2008, 5535) a Cu catalyst that effected allylic oxidation of cyclic alkenes such as 1 with high ee.

Transition Metal-Mediated Construction of Carbocycles: Dimethyl Gloiosiphone A (Takahashi), Pasteurestin A (Mulzer), and Pentalenene (Fox)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Transition Metal ◽  
South Florida ◽  
Health Science ◽  
Pt Catalyst ◽  
Max Planck ◽  
Au Catalyst ◽  
Ru Catalyst ◽  
National University ◽  
Rh Catalyst ◽  
The University

There continue to be new developments in transition metal- and lanthanide-mediated construction of carbocycles. Although a great deal has been published on the asymmetric cyclopropanation of styrene, relatively little had been reported for other classes of alkenes. Tae-Jeong Kim of Kyungpook National University has devised (Tetrahedron Lett. 2007, 48, 8014) a Ru catalyst for the cyclopropanation of simple α-olefins such as 1. X. Peter Zhang of the University of South Florida has developed (J. Am.Chem. Soc. 2007, 129, 12074) a Co catalyst for the cyclopropanation of alkenes such as 5 having electron-withdrawing groups. Alexandre Alexakis of the Université de Genève has reported(Angew. Chem. Int. Ed. 2007, 46, 7462) simple monophosphine ligands that enabled enantioselective conjugate addition to prochiral enones, even difficult substrates such as 8. Seunghoon Shin of Hanyang University has found (Organic Lett. 2007, 9, 3539) an Au catalyst that effected the diastereoselective cyclization of 10 to the cyclohexene 11, and Radomir N. Saicic of the University of Belgrade has carried out (Organic Lett. 2007, 9, 5063), via transient enamine formation, the diastereoselective cyclization of 12 to the cyclohexane 13. Alois Fürstner of the Max-Planck- Institut, Mülheim has devised (J. Am. Chem. Soc. 2007, 129, 14836) a Rh catalyst that cyclized the aldehyde 14 to the cycloheptenone 15. Some of the most exciting investigations reported in recent months have been directed toward the direct diastereo- and enantioselective preparation of polycarbocyclic products. Rai-Shung Liu of National Tsing-Hua University has extended (J. Org. Chem. 2007, 72, 567) the intramolecular Pauson-Khand cyclization to the epoxy enyne 16, leading to the 5-5 product 17. Michel R. Gagné of the University of North Carolina has devised (J. Am. Chem. Soc. 2007, 129, 11880) a Pt catalyst that smoothly cyclized the polyene 18 to the 6-6 product 19. Yoshihiro Sato of Hokkaido University and Miwako Mori of the Health Science University of Hokkaido have described (J. Am. Chem. Soc. 2007, 129, 7730) a Ru catalyst for the cyclization of 20 to the 5-6-5 product 21. Each of these processes proceeded with high diastereocontrol.

Intramolecular Diels-Alder Cycloaddition: Brombyin II (Lygo), Ptilocaulin (Livinghouse), Bistellettadine A (Snider), (-)-Pycnanthuquinone C (Trauner), (+)-Caribenol A (Li/Yang)

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Diels Alder ◽  
Thermal Cyclization ◽  
State University ◽  
Natural Form ◽  
Metal Catalysis ◽  
Montana State University ◽  
University Of Munich ◽  
Peking University ◽  
Rh Catalyst ◽  
The University

The biosynthesis of brombyin III 2 and brombyin II 3, racemic in their natural form, might logically be expected to proceed by thermal cyclization of 1. Barry Lygo of the University of Nottingham observed (Synlett 2010, 618) that the cyclization of 1 in toluene required 165°C. It is intriguing that on water in the presence of the detergent SDS, the cyclization proceeded smoothly at only slightly above ambient temperature. Intramolecular Diels-Alder cycloaddition can also be promoted by transition metal catalysis. Tom Livinghouse of Montana State University optimized (Synlett 2010, 247) a Rh catalyst for the diastereoselective cyclization of the highly substituted Z -triene 4 to 5, setting the stage for the synthesis of ptilocaulin 6. It seemed plausible that the biosynthesis of bistellettadine A 9 was proceeding by intermolecular dimerization of the monomeric carboxylic acid corresponding to 7. Barry B. Snider of Brandeis University found (Org. Lett. 2010, 12, 828) that intermolecular dimerization did proceed efficiently, but gave a 5:4 mixture of diastereomers. In contrast, the linked diester 7 cyclized with exclusive diastereocontrol. The product 8 was readily carried on to bistellettadine A 9. This raises the possibility that a chiral template, attached either covalently or through salt formation, could be designed that would direct the absolute configuration of the cycloaddition. It also seemed plausible that (-)-pycnanthuquinone 13 could be derived biosynthetically by cycloaddition of a triene 12, with one of the alkenes of the diene incorporated in a quinone. Dirk Trauner of the University of Munich prepared (Angew. Chem. Int. Ed. 2010, 49, 6199) 12 by Heck coupling of the bromide 10 with commercial linalool 11. In mixed water/ toluene, the cyclization was followed by the addition of water and reoxidation, to directly deliver (-)-pycnanthuquinone 13. Related quinone cycloadditions have been reported (Org. Lett. 2010, 12, 5554; Tetrahedron Lett. 2010, 51, 5116). Chuang-Chuang Li of the Shenzhen Graduate School and Zhen Yang of Peking University anticipated (J. Am. Chem. Soc. 2010, 132, 13608) that it would be possible to prepare (+)-caribenol A 16 by the cyclization of the alkyne 14. Direct thermal cyclization of 14 was not effective, nor were Lewis acid catalysts.

Metal Mediated C-C Ring Construction:The Nevado Route to (-)- Frondosin A

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Oxidative Coupling ◽  
Gold Catalyst ◽  
University Of California ◽  
Terminal Alkyne ◽  
University Of Utah ◽  
University Of Wisconsin ◽  
Peking University ◽  
University Of Zurich ◽  
The University ◽  
University Of Manchester

Barry M. Trost of Stanford University generated (J. Am. Chem. Soc. 2011, 133, 4766) a β-keto carbene from the propargyl alcohol 1, leading to the cyclopropane 2. Tsutomu Katsuki of Kyushu University devised (J. Am. Chem. Soc. 2011, 133, 170) an Ir catalyst for the enantioselective cyclopropenation of a terminal alkyne 3 to give 5. David J. Procter of the University of Manchester showed (Org. Lett. 2010, 12, 5446) that the SmI2 -mediated cyclization of 6 proceeded with high diastereocontrol. F. Dean Toste of the University of California, Berkeley, developed (J. Am. Chem. Soc. 2011, 133, 5500) a gold catalyst for the enantioselective cyclization of 8 to 9. Jon D. Rainier of the University of Utah found (Org. Lett. 2011, 13, 700) that the readily prepared diazo ester 10 cyclized smoothly to 11. Brian M. Stoltz of Caltech rearranged (Angew. Chem. Int. Ed. 2011, 50, 2756) 12, prepared by enantioselective allylation, to the cyclopentene 13. Tushar Kanti Chakraborty of the Indian Institute of Chemical Technology cyclized (Tetrahedron Lett. 2011, 52, 1709) the epoxy ester 14 to the cyclopentanol 15. Zhi-Xiang Yu of Peking University found (Angew. Chem. Int. Ed. 2011, 50, 2144) that a BINOL-derived catalyst cyclized 16 to 17. Related transition metal-mediated cyclizations (not illustrated) have been reported (Org. Lett. 2011, 13, 1517, 2630). Pher G. Andersson of Uppsala University reduced (Chem. Commun. 2011, 47, 3989) the inexpensive Birch reduction product 18 to give, after hydrolysis, the cyclohexanone 19 in high ee. Silas P. Cook of the University of Indiana found (Org. Lett. 2011, 13, 1904) conditions for the allylation of the Zn enolate resulting from enantioselective conjugate addition to cyclohexenone 20. This approach worked for other ring sizes as well. Weiping Tang of the University of Wisconsin effected (Angew. Chem. Int. Ed. 2011, 50, 1346) regioselective cyclocarbonylation of 22 to give the cyclohexanone 23. Ken Tanaka of the Tokyo University of Agriculture and Technology devised (Angew. Chem. Int. Ed. 2011, 50, 1664) a spectacular three-component coupling leading, after oxidative coupling, to the cyclohexane 26. Cristina Nevada of the University of Zurich condensed (Angew. Chem. Int. Ed. 2011, 50, 911) 27 with 28 to give, after methanolysis, the cycloheptanone 29 in high ee.

scholarly journals Changes of air quality during the pandemic and airborne transmission issues

2020 ◽  
Author(s):  
Weijie Zhao
Keyword(s):  
Air Quality ◽  
Large Scale ◽  
Panel Discussion ◽  
Max Planck ◽  
Airborne Transmission ◽  
Atmospheric Sciences ◽  
Work From Home ◽  
University Of Technology ◽  
Peking University ◽  
Controlling Measures

Abstract The COVID-19 pandemic has killed more than 1 000 000 people within nine months in 2020. The world is changed as the cities were locked down, the traffic reduced, and people forced to work from home and keep social distance. These controlling measures also resulted in drastic reduction of the emission of many air pollutants, providing researchers an unprecedented large-scale natural experiment in examining how the air quality would respond to a strong forcing. In this panel discussion held on 22 September 2020, five experts gathered to discuss their observations and analyses, as well as the current understanding and misconception about airborne transmission. This Forum article is dedicated to Prof. Martin Williams of the Imperial College London, who intended to join the panel discussion but passed away one day before it. Guy Brasseur Professor of Max Planck Institute for Meteorology, Germany Junji Cao Professor of Institute of Earth Environment, Chinese Academy of Sciences, China Aijun Ding Dean and Professor of School of Atmospheric Sciences, Nanjing University, China Lidia Morawska Professor of Queensland University of Technology, Australia Tong Zhu (Chair) Dean and Professor of College of Environmental Sciences and Engineering, Peking University, China

Substituted Benzenes: The Subba Reddy Synthesis of 7-Desmethoxyfusarentin

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Ethyl Cyanoacetate ◽  
Strong Acid ◽  
State University ◽  
Max Planck ◽  
University Of Texas ◽  
Ru Catalyst ◽  
Aryl Ketones ◽  
Peking University ◽  
University Of Bristol ◽  
The University

Andrey P. A ntonchick of the Max-Planck-Institut Dortmund devised (Org. Lett. 2012, 14, 5518) a protocol for the direct amination of an arene 1 to give the amide 3. Douglass A. Klumpp of Northern University showed (Tetrahedron Lett. 2012, 53, 4779) that under strong acid conditions, an arene 4 could be carboxylated to give the amide 6. Eiji Tayama of Niigata University coupled (Tetrahedron Lett. 2012, 53, 5159) an arene 7 with the α-diazo ester 8 to give 9. Guy C. Lloyd-Jones and Christopher A. Russell of the University of Bristol activated (Science 2012, 337, 1644) the aryl silane 11 to give an intermediate that coupled with the arene 10 to give 12. Ram A. Vishwakarma and Sandip P. Bharate of the Indian Institute of Integrative Medicine effected (Tetrahedron Lett. 2012, 53, 5958) ipso nitration of an areneboronic acid 13 to give 14. Stephen L. Buchwald of MIT coupled (J. Am. Chem. Soc. 2012, 134, 11132) sodium isocyanate with the aryl chloride 15 (aryl triflates also worked well) to give the isocyanate 16, which could be coupled with phenol to give the carbamate or carried onto the unsymmetrical urea. Zhengwu Shen of the Shanghai University of Traditional Chinese Medicine used (Org. Lett. 2012, 14, 3644) ethyl cyanoacetate 18 as the donor for the conversion of the aryl bromide 17 to the nitrile 19. Kuo Chu Hwang of the National Tsig Hua University showed (Adv. Synth. Catal. 2012, 354, 3421) that under the stimulation of blue LED light the Castro-Stephens coupling of 20 with 21 proceeded efficiently at room temperature. Lutz Ackermann of the Georg-August-Universität Göttingen employed (Org. Lett. 2012, 14, 4210) a Ru catalyst to oxidize the amide 23 to the phenol 24. Both Professor Ackermann (Org. Lett. 2012, 14, 6206) and Guangbin Dong of the University of Texas (Angew. Chem. Int. Ed. 2012, 51, 13075) described related work on the ortho hydroxylation of aryl ketones. George A. Kraus of Iowa State University rearranged (Tetrahedron Lett. 2012, 53, 7072) the aryl benzyl ether 25 to the phenol 26. The synthetic utility of the triazene 27 was demonstrated (Angew. Chem. Int. Ed. 2012, 51, 7242) by Yong Huang of the Shenzen Graduate School of Peking University.

Enantioselective Construction of Alkylated Stereogenic Centers

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Ni Catalyst ◽  
Max Planck ◽  
Enantiomerically Pure ◽  
University Of Oxford ◽  
Princeton University ◽  
Oxidation Reduction ◽  
Single Diastereomer ◽  
Rh Catalyst ◽  
The University ◽  
Diastereomeric Excess

Carsten Bolm of RWTH Aachen developed (Angew. Chem. Int. Ed. 2008, 47, 8920) an Ir catalyst that effected hydrogenation of trisubstituted enones such as 1 with high ee. Benjamin List of the Max-Planck-Institut Mülheim devised (J. Am. Chem. Soc. 2008, 130, 13862) an organocatalyst for the enantioselective reduction of nitro acrylates such as 3 with the Hantzsch ester 4. Gregory C. Fu of MIT optimized (J. Am. Chem. Soc. 2008, 130, 12645) a Ni catalyst for the enantioselective arylation of propargylic halides such as 6. Both enantiomers of 6 were converted to the single enantiomer of 8. Michael C. Willis of the University of Oxford established (J. Am. Chem. Soc. 2008, 130, 17232) that hydroacylation with a Rh catalyst was selective for one enantiomer of the allene 9, delivering 11 in high ee. Similarly, José Luis García Ruano of the Universidad Autónoma de Madrid found (Angew. Chem. Int. Ed. 2008, 47, 6836) that one enantiomer of racemic 13 reacted selectively with the enantiomerically- pure anion 12, to give 14 in high diastereomeric excess. Ei-chi Negishi of Purdue University described (Organic Lett. 2008, 10, 4311) the Zr-catalyzed asymmetric carboalumination (ZACA reaction) of the alkene 15 to give the useful chiron 16. David W. C. MacMillan of Princeton University developed (Science 2008, 322, 77) an intriguing visible light-powered oxidation-reduction approach to enantioselective aldehyde alkylation. The catalytic chiral secondary amine adds to the aldehyde to form an enamine, that then couples with the radical produced by reduction of the haloester. Two other alkylations were based on readily-available chiral auxiliaries. Philippe Karoyan of the Université Pierre et Marie Curie observed (Tetrahedron Lett . 2008, 49, 4704) that the acylated Oppolzer camphor sultam 20 condensed with the Mannich reagent 21 to give 22 as a single diastereomer. Andrew G. Myers of Harvard University developed the pseudoephedrine chiral auxiliary of 23 to direct the construction of ternary alkylated centers. He has now established (J. Am. Chem. Soc. 2008, 130, 13231) that further alkylation gave 24, having a quaternary alkylated center, in high diastereomeric excess.

Construction of Alkenes, Alkynes and Allenes

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Cation Exchange Resin ◽  
Terminal Alkyne ◽  
Amberlyst 15 ◽  
University Of Oxford ◽  
University Of British Columbia ◽  
University Of Louisville ◽  
Rh Catalyst ◽  
Institute Of Technology ◽  
The University ◽  
Trisubstituted Alkenes

Products such as 3 and 6 are usually prepared by phosphonate condensation. J. S. Yadav of the Indian Institute of Technology, Hyderabad found (Tetrahedron Lett. 2008, 49, 4498) that the cation-exchange resin Amberlyst-15 in CH2Cl2 mediated the condensation of a terminal alkyne such as 1 with an aldehyde to give the enone 3. Similarly, Teruaki Mukaiyama of Kitasato University showed (Chemistry Lett. 2008, 37, 704) that tetrabutylammonium acetate mediated the condensation of 5 with an aldehyde such as 4 to give the ester 6. David M. Hodgson of the University of Oxford described (J. Am. Chem. Soc. 2008, 130, 16500) the optimization of the Schlosser protocol for the condensation of a phosphorane with an aldehyde 7 followed by deprotonation and halogenation, to deliver the alkenyl halide 9 with good geometric control. Jun Terao of Kyoyo University and Nobuaki Kambe of Osaka University accomplished (Chem. Commun. 2008, 5836) the homologation of a halide such as 10 to the corresponding allylic Grignard reagent 12. Primary, secondary and tertiary halides worked well. Jennifer Love of the University of British Columbia developed (Organic Lett. 2008, 10, 3941) a Rh catalyst for the addition of thiols to terminal alkynes such as 13, and found that the product thioether 14 coupled smoothly with Grignard reagents to deliver the 1,1-disubstituted alkene 15. Glenn C. Micalizio, now at Scripps Florida, established (J. Am. Chem. Soc. 2008, 130, 16870) what appears to be a general method for the construction of Z-trisubstituted alkenes such as 18. The Ohira protocol has become the method of choice for converting an aldehyde 19 to the alkyne 21. We have found (Tetrahedron Lett. 2008, 49, 6904) that the reagent 20 offers advantages in price, preparation and handling. Bo Xu and Gerald B. Hammond of the University of Louisville observed (Organic Lett. 2008, 10, 3713) that an allene ester such as 22 is readily homologated to the alkyne 23. Ashton C. Partridge of Massey University extended (Tetrahedron Lett. 2008, 49, 5632) condensation with the aryl phosphonate 25 to porphyrin aldehydes, leading to alkynes such as 26.

A stable rhodium single-site catalyst encapsulated within dendritic mesoporous nanochannels

Nanoscale ◽  
2018 ◽  
Vol 10 (3) ◽  
pp. 1047-1055 ◽  
Author(s):  
Jun Tian ◽  
Dali Yang ◽  
Jianguo Wen ◽  
Alexander S. Filatov ◽  
Yuzi Liu ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Three Dimensional ◽  
Single Site ◽  
Terminal Alkyne ◽  
Silica Nanospheres ◽  
Excellent Activity ◽  
Rh Catalyst ◽  
Mesoporous Silica Nanospheres

A stable single-site Rh catalyst was formed inside individual channels of three-dimensional dendritic mesoporous silica nanospheres through aminosilane binding. The catalyst demonstrated an excellent activity, stability and recyclability in the reduction of 4-nitrophenol, high regioselectivity in the hydrosilylation of terminal alkyne.

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