Best Synthetic Methods: Oxidation and Reduction

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Synthetic Methods ◽  
Terminal Alkyne ◽  
University Of Kansas ◽  
University Of Mississippi ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Aldehydes And Ketones ◽  
The University ◽  
Technological University ◽  
Trisubstituted Alkenes

Johannes G. de Vries of DSM Pharmaceuticals prepared (Chem. Commun. 2009, 3747) Fe nanoparticles that selectively mediated the hydrogenation of Z alkenes and not trisubstituted alkenes. This should allow the conversion of 1 to 2. In the course of a synthesis (Tetrahedron Lett. 2009, 50, 4368) of centrolobine, Teck-Peng Loh of Nanyang Technological University employed an elegant protocol for the reduction of the secondary bromide 3. István Markó of the Université catholique de Louvain observed (Tetrahedron 2009, 65, 10930) that toluates such as 5 can be reduced smoothly with SmI2 to the corresponding C-H. Dan Yang of the University of Hong Kong devised (Organic Lett. 2009, 11, 3302) a triethylsilane-based procedure for the reductive amination of aldehydes and ketones such as 7. Jon A. Tunge of the University of Kansas developed (J. Am. Chem. Soc. 2009, 131, 16626) a complementary protocol for the conversion of an aldehyde or ketone to the protected amine 12. Mark T. Hamann of the University of Mississippi established (Tetrahedron Lett. 2009, 50, 3901) that a nitroaromatic 13 could be reduced in the presence of an acid chloride 14 to deliver the amide 15 directly. Matthias Beller of the Universität Rostock (Angew. Chem. Int. Ed. 2009, 48, 9507) and Hideo Nagashima of Kyushu University (Angew. Chem. Int. Ed. 2009, 48, 9511; J. Am. Chem. Soc. 2009, 131, 15032) reported parallel investigations of the silane-based reduction of an amide 16 to the amine 17. Xue-Long Hou of the Shanghai Institute of Organic Chemistry demonstrated (Tetrahedron Lett. 2009, 50, 5578) that a terminal alkyne 18 could be oxidized to the α-acetoxy ketone 19. Philippe Renaud of the Universität Bern and Armido Studer of West fälische-Wilhelms-Universität established (Angew. Chem. Int. Ed. 2009, 48, 6037) that both zinc enolates and silyl enol ethers could combine with chlorocatechol borane followed by TEMPO to give the α-oxygenated ketone. Stephen P. Marsden of the University of Leeds devised (Tetrahedron Lett. 2009, 50, 6106) a protocol for oxidizing a primary amine 18 to the benzoxazole 24, which has the oxidation state of the carboxylic acid.

Best Synthetic Methods: Carbon-Carbon Bond Construction

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Amino Acids ◽  
Synthetic Methods ◽  
University Of Kansas ◽  
Max Planck ◽  
Cornell University ◽  
Carbon Carbon Bond ◽  
Terminal Alkene ◽  
Sequential Coupling ◽  
The University ◽  
Trisubstituted Alkenes

In the context of peptidyl ketone synthesis, Troels Skrydstrup of the University of Aarhus developed (J. Org. Chem. 2008, 73, 1088) the elegant SmI2-mediated conjugate addition of acyl oxazolidinones such as 1 to acceptors such as 2. Sadagopan Raghavan of the Indian Institute of Chemical Technology, Hyderabad reported (Tetrahedron Lett. 2008, 49, 1601) that the addition of a Pummerer intermediate, generated by exposure of 4 to TFAA, to the terminal alkene 5 and SnCl4 led to efficient C-C bond formation, to give the sulfide 6 as a single (unassigned) diastereomer. Pd-catalyzed carbonylation of aryl halides and triflates is a well-established process. Stephen L. Buchwald of MIT has now (J. Am. Chem. Soc. 2008, 130, 2754) extended this transformation to much less expensive tosylates and mesylates such as 7. β-Amino acids have often been prepared from α-amino acids by Arndt-Eistert homologation. Geoffrey W. Coates of Cornell University has devised (Angew. Chem. Int. Ed. 2008, 47, 3979) a more practical alternative, the direct Co-catalyzed carbonylation of an oxazoline 9 to the 2-oxazine-6-one 10. Eiji Shirakawa and Tamio Hayashi of Kyoto University also used (Chem. Lett . 2008, 37, 654) a Co catalyst to promote the coupling of aryl and alkenyl Grignard reagents with enol trifl ates such as 11. Alois Fürstner of the Max-Planck-Institut, Mülheim optimized (Chem. Commun. 2008, 2873) promoters for the Pd-catalyzed Stille-Migata coupling of iodo alkenes such as 14 with alkenyl stannanes such as 15 to give 16. It is particularly noteworthy that their system is fluoride free. The stereocontrolled construction of trisubstituted alkenes continues to be challenging. We described (J. Org. Chem. 2008, 73, 1605) the facile preparation of the diioide 18 from the inexpensive 2-butyn-1,4-diol 17 . Sequential coupling of 18 with an aryl Grignard followed by CH3 Li delivered 19. Brian S. J. Blagg of the University of Kansas established (Tetrahedron Lett . 2008, 49, 141) that Still-Genari homologation of 20 with 21 gave (E)- 22 with high geometric control. Biao Jiang of the Shangahi Institute of Organic Chemistry reported (Organic Lett. 2008, 10, 593) a convenient alternative protocol to give ( Z )-α- bromo unsaturated esters.

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.

Best Synthetic Methods: Reactions of Alkenes

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Synthetic Methods ◽  
University Of Central Florida ◽  
Central Florida ◽  
Osaka Prefecture ◽  
Markovnikov Addition ◽  
The University ◽  
Technological University ◽  
Epoxidation Of Alkenes ◽  
Structure Of Matter ◽  
Catalyzed Oxidation

Swadeshmukul Santra of the University of Central Florida described (Tetrahedron Lett. 2009, 50, 124) a simple preparation of silica nanoparticles that efficiently catalyzed the anti-Markovnikov addition of thiophenol to alkenes (illustrated) and also to alkynes. Akiya Ogawa of Osaka Prefecture University devised (Tetrahedron Lett. 2009, 50, 624) a protocol for the photoinduced hydrophosphinylation of an alkene 3 to the phosphine oxide 4. Xavi Ribas and Miquel Costas of the University of Girona developed (Adv. Synth. Cat. 2009, 351, 348) a manganese catalyst for the epoxidation of alkenes with 30% H2O2. Masahito Ochiai of the University of Tokushima established (J. Am. Chem. Soc. 2009, 131, 1382) an iodoarene-catalyzed oxidation of an alkene 7 to the keto acid 9. If, as is likely, isolated alcohols are stable under these conditions, this will be a useful complement to RuO4 cleavage. Several methods are available for homologating unactivated alkenes. Sven Doye of the Universität Oldenburg observed (Angew. Chem. Int. Ed. 2009, 48, 1153) that a Ti catalyst could effect the addition of N-methyl aniline 10 to the alkene 3, to give the branched product 11 . The reaction also worked well in an intramolecular sense. Note that in this process, a C-H bond is also converted to a C-C bond. Kiyoshi Tomioka of Kyoto University reported (Organic Lett. 2009, 11, 2007) that the Suzuki coupling of the hydroboration product from 12 with the iodo alkene 13 was best supported by AsPh3. Teck-Peng Loh of Nanyang Technological University showed (J. Am. Chem. Soc. 2009, 131, 1372) that the homologation of an isolated alkene 15 with an acrylate ester 16 could also be carried out under oxidative conditions to give the diene 17. Weiping Su of the Fujian Institute of Research on the Structure of Matter found (Organic Lett. 2009, 11, 2341) that similar oxidative conditions effected the decarboxylative addition of an aromatic acid such as 18 to an alkene to give the substituted styrene 19. Kian L. Tan of Boston College took advantage (Organic Lett. 2009, 11, 2764) of a chelating ligand to direct the regioselective hydroformylation of an allylic sulfonamide 20. Isolated internal alkenes were stable under these conditions.

scholarly journals Synthesis of Azulene Derivatives from 2H-Cyclohepta[b]furan-2-ones as Starting Materials: Their Reactivity and Properties

2021 ◽  
Vol 22 (19) ◽  
pp. 10686
Author(s):  
Taku Shoji ◽  
Shunji Ito ◽  
Masafumi Yasunami
Keyword(s):  
Organic Materials ◽  
Synthetic Methods ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Potential Applications

A variety of synthetic methods have been developed for azulene derivatives due to their potential applications in pharmaceuticals and organic materials. Particularly, 2H-cyclohepta[b]furan-2-one and its derivatives have been frequently used as promising precursors for the synthesis of azulenes. In this review, we describe the development of the synthesis of azulenes by the reaction of 2H-cyclohepta[b]furan-2-ones with olefins, active methylenes, enamines, and silyl enol ethers as well as their reactivity and properties.

Best Synthetic Methods: Reduction

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Simple Procedure ◽  
Selective Reduction ◽  
Ethyl Acrylate ◽  
High Reactivity ◽  
Synthetic Methods ◽  
Ru Complex ◽  
Aldehydes And Ketones ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
The University

Heshmatollah Alinezhad of Mazandaran University, Iran. developed (Tetrahedron Lett. 2009, 50, 659) the reagent 3, a white powder that is stable for many months, as a hydride donor for the reductive amination of aldehydes and ketones. Jean-Marc Campagne of the Institut Charles Gephardt Montpellier established (Synlett 2009, 276) a simple microwave protocol for reducing aldehydes and ketones to the corresponding hydrocarbons that looks general enough to become the method of choice for this important transformation. Joanne E. Harvey of Victoria University of Wellington, in the course of a total synthesis of Aigialomycind D, observed (J. Org. Chem. 2009, 74, 2271) that despite the high reactivity of the monosubstituted alkene of 7, the conjugated alkene could be selectively reduced. Brian S. Bodnar of SiGNa Chemistry described (J. Org. Chem. 2009, 74, 2598) a simple procedure for the reduction of an ester such as 9 to the alcohol 10, using Na dispersed on silica gel. Takao Ikariya of the Tokyo Institute of Technology designed (Angew. Chem. Int. Ed. 2009, 48, 1324) a Ru complex for the hydrogenation of N-acylsulfonamides and N-acylcarbamates such as 11 to the corresponding alcohol, 12. Remarkably, Hideo Nagashima of Kyushu University demonstrated (Chem. Commun. 2009, 1574) that even in the presence of the ester, the amide of 13 could be selectively reduced to the enamine 14. The enamine could be hydrolyzed to the aldehyde or reduced to the amine, but it is also an activated intermediate, for instance, for Michael addition to ethyl acrylate or methyl vinyl ketone. Diimide (HN=NH) is a useful reagent for selective reduction, as illustrated by the conversion of 15 to 17 . David R. Carbery of the University of Bath devised (J. Org. Chem. 2009, 74, 3186) a convenient procedure for the in situ generation of diimide from 16 and hydrazine hydrate. The reductive cleavage of tertiary nitriles to the corresponding hydrocarbon under dissolving metal conditions has been known for some time (J. Org. Chem. 1996, 61, 4219). Reduction of secondary nitriles required more forcing conditions, with K metal and crown ether (Tetrahedron Lett. 1985, 26, 6103).

Sign in / Sign up

Export Citation Format

Share Document