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Phosphine-Catalyzed Aryne Oligomerization: Direct Access to α,ω-Bisfunctionalized Oligo(ortho-arylenes)
A phosphine-catalyzed oligomerization of arynes using selenocyanates was developed. The use of JohnPhos as a bulky phosphine is the key to accessing α,ω-bisfunctionalized oligo(ortho-arylenes) with RSe as the substituent at one terminus and CN as the substituent at the other. The in situ formation of R3PSeR′ cations, serving as sterically encumbered electrophiles, hinders the immediate reaction that affords the 1,2-bisfunctionalization product and instead opens a competitive pathway leading to oligomerization. Various optimized conditions for the predominant formation of dimers, but also for higher oligomers such as trimers and tetramers, were developed. Depending on the electronic properties of the electrophilic reaction partner, even compounds up to octamers were isolated. Optimization experiments revealed that a properly tuned phosphine as catalyst is of crucial importance. Mechanistic studies demonstrated that the cascade starts with the attack of cyanide; aryne insertion into n-mers leading to (n+1)-mers was ruled out.
Bürger, Marcel,Ball, Liam T.,Barber, Thomas,Ehrhardt, Nadine,Jones, Peter G.,Namyslo, Jan C.,Werz, Daniel B.
supporting information
p. 16796 - 16803
(2021/10/20)

Nickel-Catalyzed Reversible Functional Group Metathesis between Aryl Nitriles and Aryl Thioethers
We describe a new functional group metathesis between aryl nitriles and aryl thioethers. The catalytic system nickel/dcype is essential to achieve this fully reversible transformation in good to excellent yields. Furthermore, the cyanide- and thiol-free reaction shows high functional group tolerance and great efficiency for the late-stage derivatization of commercial molecules. Finally, synthetic applications demonstrate its versatility and utility in multistep synthesis.
Delcaillau, Tristan,Boehm, Philip,Morandi, Bill
supporting information
p. 3723 - 3728
(2021/04/07)

Electrochemical C-H cyanation of electron-rich (Hetero)arenes
A straightforward method for the electrochemical C-H cyanation of arenes and heteroarenes that proceeds at room temperature in MeOH, with NaCN as the reagent in a simple, open, undivided electrochemical cell is reported. The platinum electrodes are passivated by ad-sorbed cyanide, which allows conversion of an exceptionally broad range of electron-rich substrates all the way down to dialkyl arenes. The cyanide electrolyte can be replenished with HCN, opening opportunities for salt-free industrial C-H cyanation.
Hayrapetyan, Davit,Rit, Raja K.,Kratz, Markus,Tschulik, Kristina,Goo?en, Lukas J.
supporting information
p. 11288 - 11291
(2018/10/20)

Ligand-Promoted Direct C-H Arylation of Simple Arenes: Evidence for a Cooperative Bimetallic Mechanism
A highly efficient catalyst for the direct C-H arylation of simple arenes was developed on the basis of a palladium-diimine complex. The developed catalyst exhibited the highest turnover number reported to date for the direct arylation of benzene due to increased stability provided by the diimine ligand. The reaction was also performed using only 2-3 equiv of simple arenes. Mechanistic studies in combination with kinetic measurements, isotope effect experiments, synthesis of possible intermediates, and stoichiometric reactions suggested that this reaction follows a cooperative bimetallic mechanism.
Kim, Jaewoon,Hong, Soon Hyeok
p. 3336 - 3343
(2017/06/09)

Direct C-H Cyanation of Arenes via Organic Photoredox Catalysis
Methods for the direct C-H functionalization of aromatic compounds are in demand for a variety of applications, including the synthesis of agrochemicals, pharmaceuticals, and materials. Herein, we disclose the construction of aromatic nitriles via direct C-H functionalization using an acridinium photoredox catalyst and trimethylsilyl cyanide under an aerobic atmosphere. The reaction proceeds at room temperature under mild conditions and has proven to be compatible with a variety of electron-donating and -withdrawing groups, halogens, and nitrogen- and oxygen-containing heterocycles, as well as aromatic-containing pharmaceutical agents.
McManus, Joshua B.,Nicewicz, David A.
supporting information
p. 2880 - 2883
(2017/03/11)

Transition-Metal-Free Cross-Coupling of Aryl Halides with Arylstannanes
Transition-metal-free LiCl-promoted cross-coupling reactions of tetraphenyltin, trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylstannanes with aryl halides in DMF provided access to biaryls in good to high yields. Up to four phenyl groups were transferred from the organostannanes substrates. The aryls bearing electron-withdrawing groups in either halides or organotin substrates gave coupling products in higher yields. The methodology has been applied for the efficient synthesis of ipriflavones.
He, Qing,Wang, Liwen,Liang, Yong,Zhang, Zunting,Wnuk, Stanislaw F.
p. 9422 - 9427
(2016/10/17)

PHOTOREDOX-CATALYZED DIRECT C-H FUNCTIONALIZATION OF ARENES
The invention generally relates to methods of making substituted arenes via direct C-H amination. More specifically, methods of making para- and ortho-substituted arenes via direct C-H amination are disclosed. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.
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(2017/01/31)

Azulene–Naphthalene-Type Rearrangements in Benz[a]azulene and Cyclohepta[b]indole
Flash vacuum pyrolysis (FVP) of benz[a]azulene yields phenanthrene and 2-ethynylbiphenyl. FVP of cyclohepta[b]indole similarly yields phenanthridine and 2-cyanobiphenyl. The reversibility of the reactions is demonstrated by FVP of 2-ethynylbiphenyl and 2-isocyanobiphenyl. All the observed reactions are in accord with the norcaradiene–vinylidene mechanism of the azulene–naphthalene rearrangement, whereas other proposed mechanisms are ruled out.
Wentrup, Curt,Becker, Jürgen
p. 13835 - 13839
(2016/09/21)

Generation of iminyl copper species from α-azido carbonyl compounds and their catalytic C-C bond cleavage under an oxygen atmosphere
Figure presented A copper-catalyzed reaction of α-azidocarbonyl compounds under an oxygen atmosphere is reported where nitriles are formed via C-C bond cleavage of a transient iminyl copper intermediate. The transformation is carried out by a sequence of denitrogenative formation of iminyl copper species from α-azidocarbonyl compounds and their C-C bond cleavage, where molecular oxygen (1 atm) is a prerequisite to achieve the catalytic process and one of the oxygen atoms of O2 was found to be incorporated into the β-carbon fragment as a carboxylic acid.
Chiba, Shunsuke,Zhang, Line,Ang, Gim Yean,Hui, Benjamin Wei-Qiang
supporting information; experimental part
p. 2052 - 2055
(2010/07/04)

Pd(PPh3)4-PEG 400 catalyzed protocol for the atom-efficient stille cross-coupling reaction of organotin with aryl bromides
(Chemical Equation Presented) Aryl bromides (4 equiv) were coupled efficiently with organotin (1 equiv) in an atom-efficient way using the tetra(triphenylphosphine)palladium/polyethylene glycol 400 (Pd(PPh 3)4/PEG 400) catalytic syst
Zhou, Wen-Jun,Wang, Ke-Hu,Wang, Jin-Xian
supporting information; experimental part
p. 5599 - 5602
(2009/12/03)

A new palladium catalyzed protocol for atom-efficient cross-coupling reactions of?triarylbismuths with aryl halides and triflates
A new palladium catalyzed protocol for an atom-efficient cross-coupling reaction of triarylbismuths with aryl halides and triflates has been described. The palladium catalytic system with Cs2CO3 base was found to be very efficient in DMA solvent to furnish excellent yields of cross-coupled functionalized biaryls in short reaction times.
Rao, Maddali L.N.,Jadhav, Deepak N.,Banerjee, Debasis
p. 5762 - 5772
(2008/09/21)

Iminyl radicals from α-azido o-iodoanilides via 1,5-H transfer reactions of aryl radicals: New transformation of α-azido acids to decarboxylated nitriles
(Chemical Equation Presented) The radical reaction of tributyltin hydride with o-iodo-N-methylanilides derived from α-azido acids provides an excellent access to α-(aminocarbonyl)iminyl radicals through 1,5-hydrogen transfer reaction of initially formed aryl radicals followed by β-elimination of dinitrogen from ensuing α-azido-α- (aminocarbonyl)alkyl radicals. The outcoming iminyls display a peculiar tendency to form corresponding nitriles by β-elimination of aminocarbonyl radicals.
Bencivenni, Giorgio,Lanza, Tommaso,Leardini, Rino,Minozzi, Matteo,Nanni, Daniele,Spagnolo, Piero,Zanardi, Giuseppe
p. 4721 - 4724
(2008/09/21)

New light-induced iminyl radical cyclization reactions of acyloximes to isoquinolines
An efficient photochemical approach for the unusual generation of six-membered heterocyclic rings is reported. Iminyl radicals, generated by the irradiation of acyloximes, participate in intramolecular cyclization processes and in intermolecular addition-intramolecular cyclization sequences.
Alonso, Rafael,Campos, Pedro J.,Garcia, Barbara,Rodriguez, Miguel A.
p. 3521 - 3523
(2007/10/03)

Synthesis of benzocyclic ketones via palladium-catalyzed cyclization of ω-(2-iodoaryl)alkanenitriles
An efficient procedure for the synthesis of 2,2-disubstituted benzocyclic ketones by intramolecular carbopalladation of nitriles has been developed. The cyclization of substituted 3-(2-iodoaryl)propanenitriles affords indanones in high yields. The reactio
Pletnev, Alexandre A.,Larock, Richard C.
p. 2133 - 2136
(2007/10/03)

Carbopalladation of nitriles: Synthesis of benzocyclic ketones and cyclopentenones via Pd-catalyzed cyclization of ω-(2-iodoaryl)alkanenitriles and related compounds
An efficient procedure for the synthesis of 2,2-disubstituted benzocyclic ketones by intramolecular carbopalladation of nitriles has been developed. The cyclization of substituted 3-(2-iodoaryl)-propanenitriles affords indanones in high yields. The reaction is compatible with a wide variety of functional groups. This methodology has been extended to the synthesis of tetralones and cyclopentenones.
Pletnev, Alexandre A.,Larock, Richard C.
p. 9428 - 9438
(2007/10/03)

Preparation of unsymmetrical biaryls via palladium-catalyzed coupling reaction of aryl halides
The synthesis of unsymmetrical biaryls is achieved using Pd(OAc)2 as the catalyst. A great variety of aryl halides having electron withdrawing and electron donating functional groups in para, meta and ortho positions have been successfully coupled.
Hassan, Jwanro,Hathroubi, Chokri,Gozzi, Christel,Lemaire, Marc
p. 7845 - 7855
(2007/10/03)

Synthesis of unsymmetrical biaryls via palladium-catalyzed coupling reaction of aryl halides
Unsymmetrical biaryls bearing electron-donating and electron-withdrawing functional groups have been obtained in an efficient manner by Pd-catalyzed coupling of aryl halides. Aryl bromides react with aryl iodides to yield unsymmetrical biaryls with marked selectivity. (C) 2000 Elsevier Science Ltd.
Hassan,Hathroubi,Gozzi,Lemaire
p. 8791 - 8794
(2007/10/03)

Thermal ring enlargement of aromatic cyclopentadienylidene iminyl radicals. Intramolecular radical addition to the N atom of nitriles results in high yields of aza-aromatics
It has been demonstrated that ketiminyl radicals, formed at high temperatures (1000 °C, 0.3 s) in oxygen-free nitrogen from phenylhydrazones of benz-anellated cyclopentadienones (fluorenone (9a), methanophenanthrenone (9b)), yield into phenanthridine (8a) and benzo[lmn]-phenanthridine (8b) in yields > 60%. The results point to a predominant addition of intermediately generated phenyl type radicals 5 to the N atom of the nitrile groups followed by bimolecular H-abstraction of the cyclic imidoyl radicals to 8.
Hofmann, Joerg,Schulz, Kathrin,Zimmermann, Gerhard
p. 2399 - 2402
(2007/10/03)

Intramolecular Trapping of a Ketenimine Carbene Formed on Flash Vacuum Pyrolysis of 3-Phenylimino-3H-indazole and 3-Phenyliminoisobenzofuran-1-one
Flash vacuum pyrolysis of 3-phenylimino-3H-indazole yielded biphenylene, benzonitrile and, by loss of dinitrogen followed by intramolecular trapping of a ketenimine carbene intermediate, the isomers fluorenimine, phenanthridine and 2-phenylbenzonitrile.Pyrolysis of 3-phenyliminoisobenzofuran-1-one gave the same five products together with N-phenylphthalimide.It is proposed that the same ketenimine carbene intermediate is involved in the two reactions.Pyrolysis of 3-o-tolylimino- and 3-benzylimino-isobenzofuran-1-one led to fragmentation without intramolecular trapping.Pyrolysis of 3-t-butyliminoisobenzofuran-1-one gave o-cyanobenzoic acid.
Brown, Roger F. C.,Coulston, Karen J.,Eastwood, Frank W.
p. 47 - 60
(2007/10/02)

Photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene
Irradiation, through Pyrex, of an acetonitrile-methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and metal cyclic adducts (13-16) arising from the intermediate exciplex.There was no evidence for interaction between the two double bonds of this nonconjugated diene.The oxidation potential of 9 is high enough (>3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed.Similar irradiation of acetonitrile-methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond.The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur.In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer.There was no evidence for interaction between the two double bonds of the initially formed radical cation 10, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product.The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions.In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21 cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11 to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed.This 1,6-endo, endo cyclization of 11 cation radical must be rapid enough to compete with reaction with methanol.There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical.When the radical cation of 2,5-dimethyl-1,4-hexadiene (12 cation radical) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24).The mechanisms for these transformations are discussed.
Arnold, Donald R.,McManus, Kimberly A.,Du, Xinyao
p. 415 - 429
(2007/10/02)

Thermally Induced Fragmentation and Cyclisation of C-Azidohydrazones
C-Azidohydrazones 2 were synthesized from the corresponding C-chlorohydrazones 1 and submitted to thermal decomposition in boiling benzene.Various kinds of products were obtained due to competitive modes of evolution of first-formed nitrenes 13, namely hydrogen abstraction to form aminohydrazones 3 and benzotriazepine 8, and radical fragmentation to give ultimatively diaryls 4 and arylglyoxylate arylhydrazones 5.Ring-closed products, namely 1,2,4-triazoles 6 and imidazolones 7 were also formed.
Bruche, Luca,Garanti, Luisa,Zecchi, Gaetano
p. 619 - 624
(2007/10/02)

Vapour-phase Chemistry of Arenes. Part 13. Reactivity and Selectivity in the Gas-phase Reactions of Hydroxyl Radicals with Monosubstituted Benzenes at 563 K
The reactions of hydroxyl radicals with benzene derivates C6H5Z (Z = H, Me, F, Cl, Br, I, CF3, or CN) have been studied in a flow reactor at 563 K in nitrogen, using the thermolysis of ButOOH as a source of .OH.Under these conditions there are two product-forming pathways.The major one involves hydrogen abstraction to give aryl radicals ZC6H4. (II) as the first step; depending on Z, its displacement to form phenol may also occur.Relative rates for hydrogen abstraction were determined in competition experiments using side-chain hydrogen abstraction from added toluene as a reference.This resulted in the order (for Z =): 1,8(Me), 1.0(H), 0.47(F), 0.29(Cl), 0.34(CF3), 0.20(CN), consonant with the electrophilic nature of .OH.The site selectivity of hydrogen abstractions was determined by scavenging part of the aryl radicals (II) with iodine.A Hammett plot, using ? constants for meta and para positions, led to ρ -1.0.The features of hydrogen abstraction by .OH are discussed and compared with those for the analogous reaction of Cl.The formation of phenol was found to decrease in importance in the order F, Cl, Br, and I.This result is rationalized on a thermochemical kinetic basis.
Mulder, Peter,Louw, Robert
p. 1167 - 1174
(2007/10/02)

Phase-Transfer-Catalyzed Gomberg-Bachmann Synthesis of Unsymmetrical Biarenes: A Survey of Catalysts and Substrates
Two problems have hindered the Gomberg-Bachmann (GB) and Pschorr reactions of arenediazonium cations: the instability of the arenediazonium salts and side reactions.Arenediazonium tetrafluoroborate and hexafluorophosphate salts can be prepared in high yield and purity and can be stored safely.Unfortunately, these salts are insoluble in most nonpolar organic solvents.Crown ether complexation or other phase-transfer (pt) catalytic methodology can ameliorate this situation, and reactions conducted by the approaches outlined herein often afforded coupling or cyclization products in high yield and corresponding purity.The use of crown ethers, quarternary 'onium salts, lipophilic carboxylic acid salts, and even the polar cosolvent acetonitrile increase the utility of the ptGB reaction dramatically.Sixty examples of couplings are reported along with an assessment of selectivities.A number of examples are also presented of phase-transfer-type Pschorr cyclizations.In the latter case, the use of potassium superoxide, KO2, is introduced to suppress indazole formation.
Beadle, James R.,Korzeniowsky, Stephen H.,Rosenberg, David E.,Garcia-Slanga, Blanche J.,Gokel, George W.
p. 1594 - 1603
(2007/10/02)

Aryloxenium Ions. Generation from N-(Aryloxy)pyridinium Tetrafluoroborates and Reaction with Anisole and Benzonitrile
N-(Aryloxy)pyridinium tetrafluoroborates (4) decompose thermally at 180-200 deg C in anisole and benzonitrile to form products of intermolecular C-O-C and C-C bond formation.With anisole, diphenyl ethers (5) and hydroxybiphenyls (6) are formed; with benzonitrile, the main product is benzoxazole (14).A homolytic process was ruled out by showing that none of these products were formed when perbenzoyl p-nitrophenyl carbonate (18) was decomposed in these solvents.The main products in this case were those of homolytic phenylation (and benzoyloxylation with anisole).A concerted SN2-type heterolytic process was ruled out by showing that the nature of the substituent in the pyridine ring had no effect on the isomer ratios of 5 and 6 in the thermolysis of 4 (X = p-NO2) in anisole.The results are explained in terms of a unimolecular heterolysis of 4 to give the pyridine and aryloxenium ion 2 which now attacks solvent molecules.When an electron-withdrawing substituent is present in 2, more C-O-C than C-C products are formed in anisole.When it is absent only products of C-C bond formation are found.PhO+ is apparently electrophilic enough to attack anisole and give the four possible hydroxymethoxybiphenyls (10-13).
Abramovitch, Rudolph A.,Alvernhe, Gerard,Bartnik, Romuald,Dassanayake, Nissanke L.,Inbasekaran, Mutiah N.,Kato, Shiego
p. 4558 - 4565
(2007/10/02)

Aroyl Peroxides. Part 7. The Effects of Additives on the Thermolysis of Aroyl Peroxides in Arenes and the Elimination of Possible Complications in the Measurement of Partial Rate Factors for Phenylation
Competitive homolytic arylation of arenes has been carried out under conditions in which biaryl formation is maximised.Improved yields of biaryl were obtained with o-chloroanil, nitro- and nitroso-compounds, and transition metal salts; nitrosobenzene, pentafluoronitrosobenzene, copper(II)benzoate, and iron(III)benzoate caused nearly theoretical yields of biaryl and aroic acid.Partial rate factors, measured under such conditions, are free from uncertainties arising from the selective removal of ?-complexes by side-processes such as dimerisation.The possibility that arenes form complexes with aryl radicals or their precursors as a necessary part of the selection process between substrate molecules was not confirmed in studies of the application of the additivity principle and of the multiplication rule, and of variation in the relative concentration of the two competing arenes.The absence of any discrepancies indicates that the measured partial rate factors are not influenced by such putative complex formation.The mechanism of action of these catalysts has been investigated.
Bolton, Roger,Dailly, Bryce N.,Hirakubo, Kazuko,Lee, Kong Hung,Williams, Gareth H.
p. 1109 - 1120
(2007/10/02)

Mechanisms for Aromatic Photocyanation: Naphthalene and Biphenyl
Photocyanation of naphthalene and biphenyl has been studied in the systems ArH-KCN-aqueous CH3CN and ArH-NaCN-CH3OH.The reaction is first order in CN(-) and in ground state ArH as well as in excited ArH.The proposed mechanism involves the formation of a singlet excimer, which dissociates into radical ions before the attack of cyanide ion.Photocyanations in the presence of oxidants such as p-dicyanobenzene and persulphate ion proceed by oxidation of the singlet excited hydrocarbon to form a radical cation directly.
Bunce, Nigel J.,Bergsma, John P.,Schmidt, John L.
p. 713 - 719
(2007/10/02)