Wednesday, November 30, 2011
Fe-catalysed oxidative C–H functionalization/C–S bond formation
Haibo Wang, Lu Wang, Jinsai Shang, Xing Li, Haoyuan Wang, Jie Gui and Aiwen Lei
Chem. Commun., 2012, 48, 76-78
DOI: 10.1039/C1CC16184A
Dehydrogenation processes via C–H activation within alkylphosphines
Mary Grellier and Sylviane Sabo-Etienne
Chem. Commun., 2012, 48, 34-42
DOI: 10.1039/C1CC14676A
Transition Metal Catalyzed Denitrogenative Transannulation: Converting Triazoles into Other Heterocyclic Systems
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| Converting Triazoles into Other Heterocyclic Systems |
Tuesday, November 29, 2011
Mechanistic Analysis of Iridium(III) Catalyzed Direct C[BOND]H Arylations: A DFT Study
doi/10.1002/chem.201101532
Wednesday, November 23, 2011
Tuesday, November 22, 2011
Metal-Free Intermolecular Oxidative C–N Bond Formation via Tandem C–H and N–H Bond Functionalization
Brenton DeBoef, 2011, JACS DOI: 10.1021/ja2087085
Pd(II)-Catalyzed Enantioselective C–H Activation of Cyclopropanes
Jin-Quan Yu, 2011, JACS DOI: 10.1021/ja207607s
Silanol as a Removable Directing Group for the PdII-Catalyzed Direct Olefination of Arenes
DOI: 10.1002/chem.201103171
Friday, November 18, 2011
Iron-Catalyzed Direct Alkenylation of 2-Substituted Azaarenes with N-Sulfonyl Aldimines via C–H Bond Activation
Org. Lett., 2011, 13 (10), pp 2580–2583
Light-Harvesting Hybrid Hydrogels: Energy-Transfer-Induced Amplified Fluorescence in Noncovalently Assembled Chromophore–Organoclay Composites
The noncovalent self-assembly of chromophores in an organoclay template results in the formation of fluorescent hybrid hydrogels and films. These clay–dye hybrids act as novel supramolecular scaffolds for light-harvesting as the aminoclay (AC) templates the spatial organization of donor and acceptor molecules to promote Förster resonant energy transfer (see picture; CS=coronene salt, PS=perylene salt).
This artle also highlited in NATURE.
Thursday, November 17, 2011
Participation of Carbonyl Oxygen in Carbon–Carboxylate Bond-Forming Reductive Elimination from Palladium
Melanie S. Sanford, Organometallics, DOI: 10.1021/om200677y
Ruthenium-Catalyzed C–H/N–O Bond Functionalization: Green Isoquinolone Syntheses in Water
Lutz Ackermann, OL, 2011, DOI: 10.1021/ol202861k
Direct Functionalization of M–C (M = PtII, PdII) Bonds Using Environmentally Benign Oxidants, O2 and H2O2
Andrei N. Vedernikov, Acc. Chem. Res., 2011, DOI: 10.1021/ar200191k
Ligand-Promoted C3-Selective Arylation of Pyridines with Pd Catalysts: Gram-Scale Synthesis of (±)-Preclamol
Jin-Quan Yu, JACS, 2011, DOI: 10.1021/ja209510q
Nickel-Catalyzed Heck-Type Reactions of Benzyl Chlorides and Simple Olefins
Timothy F. Jamison, JACS, 2011, DOI: 10.1021/ja209235d
Ruthenium-Catalyzed Meta Sulfonation of 2-Phenylpyridines
Christopher G. Frost, JACS, 2011, DOI: 10.1021/ja208286b
Nickel-Catalyzed Suzuki–Miyaura Reaction of Aryl Fluorides
Naoto Chatani, JACS, 2011, DOI: 10.1021/ja207759e
Synthesis of Dragmacidin D via Direct C–H Couplings
Junichiro Yamaguchi and Kenichiro Itami, JACS, 2011, DOI: 10.1021/ja209945x
Tuesday, November 15, 2011
Tuesday, November 8, 2011
Palladium-Catalyzed Regioselective γ-Mono- and Diarylation of Acrylamide Derivatives with Aryl Halides
DOI: 10.1002/adsc.201100373
Saturday, November 5, 2011
Metal-Free C–H Cross-Coupling toward Oxygenated Naphthalene-Benzene Linked Biaryls
DOI: 10.1021/ol202632h
Bimetallic Redox Synergy in Oxidative Palladium Catalysis
Tobias Ritter. 2011, JACS, Acc. Chem. Res, DOI: 10.1021/ar2001974
Room-Temperature C–H Arylation: Merger of Pd-Catalyzed C–H Functionalization and Visible-Light Photocatalysis
Melanie S. Sanford, JACS, 2011, DOI: 10.1021/ja208068w
Friday, November 4, 2011
Stains for TLC Identification
Once a TLC has been developed, it is frequently
necessary to aid in the visualization of the components of a reaction mixture.
This is true primarily because most organic compounds are colorless.
Frequently, the organic compounds of interest contain a chromophore which may
be visualized by employing either a short or a long wave UV lamp. These lamps
may be found as part of a standard organic chemistry research or teaching lab.
Typical examples of functional groups which may be visualized through this
method are aromatic groups, a,b-unsaturated
carbonyls, and any other compounds containing extensively p-conjugated
systems. While exposing these TLC plates to UV light, you will notice that the
silica gel will fluoresce, while any organic molecule which absorbs UV light
will appear as a dark blue spot. Circling these spots gently with a dull pencil
will permit an initial method for visualization. Fortunately, there are a
number of permanent or semi-permanent methods for visualization which will not
only allow one to see these compounds but also provide a method for determining
what functional groups are contained within the molecule. This method is
referred to as staining the TLC plate, and experience will allow you to determine
what functional groups will appear as what color upon visualization. Following
is a listing of the most commonly employed stains, the kind of compounds for
which they're usually employed, and a typical recipe.
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A Note on TLC Plates
Although it should be obvious, be sure that the kind of TLC plate you are using is compatible with the stain or the conditions for its development. For instance, the inexpensive plates using a plastic polymer backing cannot be used for stains requiring heat for development. Glass backing is fine for this, but the silica gel is typically not tightly bonded to the glass, and tends to be inadvertantly scraped off very easily; thus, these are not suitable for storage following development. In our group, we use aluminum-backed plates, which are less expensive than glass, are heat-impervious, the silica gel is very tightly bound to the backing, and are so thin that, if desired, a particularly spectacular plate can be taped into your lab notebook.
The Stain List
Iodine
The staining of a TLC plate with
iodine vapor is among the oldest methods for the visualization of organic
compounds. It is based upon the observation that iodine has a high affinity
for both unsaturated and aromatic compounds.
Recipe
A chamber may be assembled as
follows: To 100 mL wide mouth jar (with cap) is added a piece of filter paper
and few crystals of iodine. Iodine has a high vapor pressure for a solid and
the chamber will rapidly become saturated with iodine vapor. Insert your TLC
plate and allow it to remain within the chamber until it develops a light
brown color over the entire plate. Commonly, if your compound has an affinity
for iodine, it will appear as a dark brown spot on a lighter brown
background. Carefully remove the TLC plate at this point and gently circle
the spots with a dull pencil. The iodine will not remain on the TLC plate for
long periods of time so circling these spots is necessary if one wishes to
refer to these TLC's at a later date.
Ultraviolet Light
Good for visualizing any
compounds which are UV-active, particularly those with extended conjugation,
aromatic rings, etc. Spot(s) must be lightly traced with a pencil while
visible, since when the UV light is removed, the spots disappear.
Ceric Ammonium Sulfate
Specifically developed for vinca alkaloids (aspidospermas). Recipe Prepare a 1% solution of of cerium (IV) ammonium sulfate in 50% phosphoric acid.
Cerium Sulfate
General stain, particularly effective for alkaloids. Recipe Prepare an aqueous solution of 10% cerium (IV) sulfate and 15% sulfuric acid.
Ferric Chloride
Excellent for phenols. Recipe Prepare a solution of 1% ferric (III) chloride in 50% aqueous methanol.
Morin Hydrate
General stain (morin is a hydroxy flavone), is fluorescently active. Recipe Prepare a 0.1% solution of morin hydrate (by weight) in methanol.
Ninhydrin
Excellent for amino acids Recipe Dissolve 1.5g ninhydrin in 100mL of n-butanol and then add 3.0mL acetic acid.
Dinitrophenylhydrazine
(DNP)
Developed mainly for aldehydes and ketones; forms the corresponding
hydrazones, which are usually yellow to orange and thus easily visualized.
Recipe
Dissolve 12g of
2,4-dinitrophenylhydrazine, 60mL of conc. sulfuric acid, and 80mL of water in
200mL of 95% ethanol.
Vanillin
Very good general stain, giving a range of colors for different spots. Recipe Prepare a solution of 15g vanillin in 250mL ethanol and 2.5mL conc. sulfuric acid.
Potassium Permanganate
This particular stain is excellent for functional groups which are sensitive to oxidation. Alkenes and alkynes will appear readily on a TLC plate following immersion into the stain and will appear as a bright yellow spot on a bright purple background. Alcohols, amines, sulfides, mercaptans and other oxidizable functional groups may also be visualized, however it will be necessary to gently heat the TLC plate following immersion into the stain. These spots will appear as either yellow or light brown on a light purple or pink background. Again it would be advantageous to circle such spots following visualization as eventually the TLC will take on a light brown color upon standing for prolonged periods of time.
Dissolve 1.5g of KMnO4,
10g K2CO3, and 1.25mL 10% NaOH in 200mL water. A
typical lifetime for this stain is approximately 3 months.
Bromocresol Green Stain
This particular stain is excellent for functional groups whose pKa is approximately 5.0 and lower. Thus, this stain provides an excellent means of selectively visualizing carboxylic acids. These will appear as bright yellow spots on either a dark or light blue background and typically, it is not necessary to heat the TLC plate following immersion. This TLC visualization method has a fairly long lifetime (usually weeks) thus, it is not often necessary to circle such spots following activation by staining.
To 100 ml of absolute ethanol is
added 0.04 g of bromocresol green. Then a 0.1 M solution of aqueous NaOH is
added dropwise until a blue color just appears in solution (the solution
should be colorless prior to addition). Ideally, these stains may be stored
in 100 mL wide mouth jars. The lifetime of such a solution typically depends
upon solvent evaporation. Thus, it would be advantageous to tightly seal such
jars in-between uses.
Cerium Molybdate Stain (Hanessian's Stain)
This stain is a highly sensitive, multipurpose (multifunctional group stain). One word of caution, very minor constituents may appear as significant impurities by employing this stain. To ensure accurate results when employing this stain, it is necessary to heat the treated TLC plate vigorously (a heat gun works well). Thus, this may not be a stain to employ if your sample is somewhat volatile. The TLC plate itself will appear as either light blue or light green upon treatment, while the color of the spots may vary (although they usually appear as a dark blue spot). Typically, functional groups will not be distinguishable based upon the color of their spots; however, it would be worth while to make a list of potential colors of various functional groups as you experience variations in colors. This may permit future correlations which may prove beneficial when performing similar chemistry on related substrates.
To 235 mL of distilled water was
added 12 g of ammonium molybdate, 0.5 g of ceric ammonium molybdate, and 15
mL of concentrated sulfuric acid. Storage is possible in a 250 mL wide mouth
jar. This stain has a long shelf-life so long as solvent evaporation is
limited. It may also prove worth while to surround the jar with aluminum foil
as the stain may be somewhat photo-sensitive and exposure to direct light may
shorten the shelf-life of this reagent. It is worth while to also mention
that it would be beneficial to circle the observed spots with a dull pencil
following heating as this stain will eventually fade on the TLC plate after a
few days.
p-Anisaldehyde Stain #1
This stain is an excellent multipurpose visualization method for examining TLC plates. It is sensitive to most functional groups, especially those which are strongly and weakly nucleophilic. It tends to be insensitive to alkenes, alkynes, and aromatic compounds unless other functional groups are present in the molecules which are being analyzed. It tends to stain the TLC plate itself, upon mild heating, to a light pink color, while other functional groups tend to vary with respect to coloration. It is recommended that a record is kept of which functional group stains which color for future reference, although these types of comparisons may be misleading when attempting to ascertain which functional groups are present in a molecule (especially in complex molecules). The shelf-life of this stain tends to be quite long except when exposed to direct light or solvent is allowed to evaporate. It is recommended that the stain be stored in a 100 mL wide mouth jar wrapped with aluminum foil to ensure a long life time. To 135 mL of absolute ethanol was added 5 mL of concentrated sulfuric acid, 1.5 mL of glacial acetic acid and 3.7 mL of p-anisaldehyde. The solution is then stirred vigorously to ensure homogeneity. The resulting staining solution is ideally stored in a 100 mL wide mouth jar covered with aluminum foil.
p-Anisaldehyde
Stain #2
A
more specialized stain than #1 (above), used for terpenes, cineoles,
withanolides, acronycine, etc. As above, heating with a heat gun must
be employed to effect visualization.
Recipe Prepare solution as follows: anisaldehyde:HClO4:acetone:water (1:10:20:80)
Phosphomolybdic Acid (PMA) Stain
Phosphomolybdic acid stain is a good "universal" stain which is fairly sensitive to low concentrated solutions. It will stain most functional groups, however it does not distinguish between different functional groups based upon the coloration of the spots on the TLC plate. Most often, TLC's treated with this stain will appear as a light green color, while compounds of interest will appear as much darker green spots. It is necessary to heat TLC plates treated with this solution in order to activate the stain for visualization. The shelf life of these solutions are typically quite long, provided solvent evaporation is kept to a minimum. Dissolve 10 g of phosphomolybdic acid in 100 mL of absolute ethanol.
Occasionally, if you find it
necessary to develop or investigate other staining techniques, the following
references may be helpful:
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Boronic Acids
Wiley: Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine and Materials, By Dennis Hall, Second, Completely Revised Edition, 2 Volume Set:
Table of Content:
Contents to Volume 1
Foreword V
Contents to Volume 2 XIII
Preface XV
List of Contributors XIX
1 Structure, Properties, and Preparation of Boronic Acid Derivatives: Overview of Their Reactions and Applications 1
Dennis G. Hall
1.1 Introduction and Historical Background 1
1.2 Structure and Properties of Boronic Acid Derivatives 2
1.3 Preparation of Boronic Acids and Their Esters 31
1.4 Isolation and Characterization 73
1.5 Overview of the Reactions of Boronic Acid Derivatives 78
1.6 Overview of Other Applications of Boronic Acid Derivatives 97
References 109
2 Metal-Catalyzed Borylation of C–H and C–Halogen Bonds of Alkanes, Alkenes, and Arenes for the Synthesis of Boronic Esters 135
Tatsuo Ishiyama and Norio Miyaura
2.1 Introduction 135
2.2 Borylation of Halides and Triflates via Coupling of H–B and B–B Compounds 137
2.3 Borylation via C–H Activation 148
2.4 Catalytic Cycle 159
2.5 Summary 161
References 161
3 Transition Metal-Catalyzed Element-Boryl Additions to Unsaturated Organic Compounds 171
Michinori Suginome and Toshimichi Ohmura
3.1 Introduction 171
3.2 Diboration 172
3.3 Silaboration 185
3.4 Carboboration 202
3.5 Miscellaneous Element-Boryl Additions 207
3.6 Conclusion 208
References 208
4 The Contemporary Suzuki–Miyaura Reaction 213
Cory Valente and Michael G. Organ
4.1 Introduction 213
4.2 Developments Made in the Coupling of Nontrivial Substrates 215
4.3 Asymmetric Suzuki–Miyaura Cross-Couplings 241
4.4 Iterative Suzuki–Miyaura Cross-Couplings 248
4.5 Conclusions and Future Outlook 256
References 257
5 Rhodium- and Palladium-Catalyzed Asymmetric Conjugate Additions of Organoboronic Acids 263
Guillaume Berthon-Gelloz and Tamio Hayashi
5.1 Introduction 263
5.2 Rh-Catalyzed Enantioselective Conjugate Addition of Organoboron Reagents 263
5.3 Pd-Catalyzed Enantioselective Conjugate Addition of Organoboron Reagents 299
5.4 Conclusions 306
References 307
6 Recent Advances in Chan–Lam Coupling Reaction: Copper-Promoted C–Heteroatom Bond Cross-Coupling Reactions with Boronic Acids and Derivatives 315
Jennifer X. Qiao and Patrick Y.S. Lam
6.1 General Introduction 315
6.2 C–O Cross-Coupling with Arylboronic Acids 316
6.3 C–N Cross-Coupling with Arylboronic Acids 321
6.4 Substrate Selectivity and Reactivity in Chan–Lam Cross-Coupling Reaction 335
6.5 C–N and C–O Cross-Coupling with Alkenylboronic Acids 336
6.6 C–N and C–O Cross-Coupling with Boronic Acid Derivatives 338
6.7 C–S and C–Se/C–Te Cross-Coupling 346
6.8 Mechanistic Considerations 349
6.9 Other Organometalloids 354
6.10 Conclusion 355
6.11 Note Added in Proof 355
References 357
Contents to Volume 2
7 Transition Metal-Catalyzed Desulfitative Coupling of Thioorganic Compounds with Boronic Acids 363
Ethel C. Garnier-Amblard and Lanny S. Liebeskind
7.1 General Introduction 363
7.2 Boronic Acid-Thioorganic C–S Desulfitative Cross-Couplings Using Catalytic Nickel or Palladium 364
7.3 Thioorganic C–S Desulfitative Cross-Couplings Using Only Catalytic Copper 380
7.4 Miscellaneous 387
7.5 Conclusions 388
References 388
8 Catalytic Additions of Allylic Boronates to Carbonyl and Imine Derivatives 393
Tim G. Elford and Dennis G. Hall
8.1 Introduction 393
8.2 Additions to Aldehydes 395
8.3 Additions to Ketones 412
8.4 Additions to Imine Derivatives 418
8.5 Conclusions 422
References 423
9 Recent Advances in Nucleophilic Addition Reactions of Organoboronic Acids and Their Derivatives to Unsaturated C–N Functionalities 427
Timothy R. Ramadhar and Robert A. Batey
9.1 Introduction 427
9.2 Recent Advances in the Petasis Borono-Mannich Reaction 428
9.3 Reactions of N-Acyliminium Ions with Organoboronic Acids and Their Derivatives 449
9.4 Advances in Metal-Catalyzed Additions with Organoboronic Acids and Their Derivatives 455
9.5 Conclusions 472
References 473
10 Asymmetric Homologation of Boronic Esters with Lithiated Carbamates, Epoxides, and Aziridines 479
Matthew P. Webster and Varinder K. Aggarwal
10.1 Introduction 479
10.2 Lithiated Primary Alkyl Carbamates for the Homologation of Boranes and Boronic Esters 481
10.3 Lithiated Secondary Carbamates for the Homologation of Boranes and Boronic Esters 492
10.4 Benzylic N-Linked Lithiated Carbamates for the Homologation of Trialkylboranes 496
10.5 Lithiated Epoxides for the Homologation of Boronic Esters 496
10.6 Lithiated Aziridines for the Homologation of Boronic Esters 500
10.7 Conclusions 501
References 502
11 Organotrifluoroborates: Organoboron Reagents for the Twenty-First Century 507
Gary A. Molander and Ludivine Jean-Gérard
11.1 Introduction 507
11.2 Synthetic Approaches to Organotrifluoroborates 508
11.3 Elaboration of Organotrifluoroborates via Transformations of Pendant Functional Groups 509
11.4 Transition Metal-Catalyzed Processes 526
11.5 Miscellaneous Reactions of Organotrifluoroborates 537
11.6 Carbon–Carbon Bond-Forming Reactions with Activated Electrophiles 542
11.7 Conclusions 546
References 546
12 Borate and Boronic Acid Derivatives as Catalysts in Organic Synthesis 551
Joshua N. Payette and Hisashi Yamamoto
12.1 Introduction 551
12.2 Nonchiral Boron-Based Catalysis 551
12.3 Chiral Boron-Based Catalysis 561
12.4 Conclusion 587
References 587
13 Applications of Boronic Acids in Chemical Biology and Medicinal Chemistry 591
Nanting Ni and Binghe Wang
13.1 Introduction 591
13.2 Boronic Acids as Potential Medicinal Agents 591
13.3 Probes for Detecting Reactive Oxygen Species 597
13.4 MRI and PET Agents for in vivo Carbohydrate Imaging 603
13.5 Carbohydrate Biomarker Binding Agents and Sensors 607
13.6 Conclusions 617
References 617
14 Boronic Acids in Materials Chemistry 621
Jie Liu and John J. Lavigne
14.1 Introduction 621
14.2 Linear Boronate-Linked Materials 624
14.3 Macrocycles and Cages 637
14.4 Networks 658
14.5 Summary and Outlook 671
References 673
Index 677
Wednesday, November 2, 2011
Highly regioselective palladium-catalysed oxidative allylic C–H carbonylation of alkenes
Chem. Commun., 2011, 47, 12224-12226
