Conjugate Addition of Acetal-Derived Benzyl Radicals Generated from Low-Valent Titanium-Mediated C–O Bond Cleavage

2021 ◽  
Author(s):  
Takuya Suga ◽  
Masaharu Nakamura ◽  
Ryusei Takada ◽  
Yutaka Ukaji
Keyword(s):  
Bond Cleavage ◽  
Conjugate Addition ◽  
Benzyl Radicals ◽  
Low Valent

Selective Bond Cleavage Reactions by Low-Valent Ruthenium Complexes

ChemInform ◽  
2003 ◽  
Vol 34 (18) ◽  
Author(s):  
Masafumi Hirano ◽  
Nobuyuki Komine ◽  
Sanshiro Komiya
Keyword(s):  
Bond Cleavage ◽  
Ruthenium Complexes ◽  
Cleavage Reactions ◽  
Low Valent

Rhodium catalyzed C–C bond cleavage/coupling of 2-(azetidin-3-ylidene)acetates and analogs

2019 ◽  
Vol 55 (84) ◽  
pp. 12707-12710 ◽  
Author(s):  
Xuan Yang ◽  
Wei-Yu Kong ◽  
Jia-Ni Gao ◽  
Li Cheng ◽  
Nan-Nan Li ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Conjugate Addition

The tandem “conjugate addition/β-C cleavage/protonation” process (CCP) is reported.

Basen-induzierte Alkin-Spaltung in W(II)-Komplexen – ein neuer Weg zu niedervalenten Carbin-Komplexen aus W(CO)6 / Base-Induced Alkyne Cleavage in W(II) ComplexesaNew Way to Low Valent Carbyne Complexes from W(CO)6

1990 ◽  
Vol 45 (3) ◽  
pp. 351-368 ◽  
Author(s):  
Alexander Constantin Filippou ◽  
Christian Völkl ◽  
Walter Grünleitner ◽  
Paul Kiprof
Keyword(s):  
Bond Cleavage ◽  
Nucleophilic Attack ◽  
Monoclinic Space Group ◽  
High Electron ◽  
Hindered Rotation ◽  
Isocyanide Ligands ◽  
Single Transition ◽  
Low Valent ◽  
Alkyne Complexes ◽  
Carbyne Complexes

A new entry to low-valent, carbonyl-free tungsten phenylcarbyne complexes has been developed from W(CO)6 via tungsten(II) alkyne complexes. The first step includes thermal decarbonylation of W(CO)6 to fac-W(CO)3(MeCN)3 and subsequent substitution of the acetonitrile ligands by EtNC or t-BuNC to give fac-W(CO)3(EtNC)3 (1 a) or fac-W(CO)3(t-BuNC)3 (1 b) in almost quantitative yields. Advantages of this indirect synthesis of 1 a and 1 b from W(CO)6 are discussed in comparison to the previously described, CoCl2 catalyzed transformation of W(CO)6 with RNC to fac-W(CO)3(RNC)3. Compounds 1 a and 1 b are then quantitatively converted with Br2 to W(CO)2(EtNC)3(Br)2 (2 a) and W(CO)2(t-BuNC)3(Br)2 (2b). 2 a and 2b react subsequently with PhC=CBr to give upon elimination of both CO ligands the carbonylfree compounds W(EtNC)3(η2-PhC=CBr)(Br)2 (3a) and W(t-BuNC)3(η2-PhC=CBr)(Br)2 (3b) in good yield. 3 a and 3b represent rare examples of complexes containing a 1-haloalkyne ligand. They are susceptible to nucleophilic attack at this ligand. Thus reaction of 3 a and 3 b witht-BuNH2 or Et2NH gives the 1-aminoalkyne complexes W(EtNC)3[η2-PhC=CNH(t-Bu)](Br)2 (4a), W(t-BuNC)3[η2-PhC≡CNH(t-Bu)](Br)2 (4 b) and W(t-BuNC)3(η2-PhC=CNEt2)(Br)2 (4c) in good yields. Finally a base-induced cleavage of the alkyne ligand is achieved in 4 a and 4b using LiPh and gives the carbyne complexes mer,trans-Br(t-BuNC)(EtNC)3W=CPh (5a) and trans-Br(t-BuNC)4W=CPh (5b). This decoupling reaction is the first example of an alkyne-bond cleavage to C1-fragments at a single transition metal center and the key step in the new synthetic procedure to 5 a and 5 b from W(CO)6. Complex 5 b has been previously prepared from W(CO)6 by the classical Fischer route via the carbonyl containing carbyne complextrans-Br(CO)4W=CPh and has been shown to undergo the reverse of the decoupling reaction i.e. an H Br-induced coupling of a tert-butylisocyanide with the phenylcarbyne ligand to form 4b. The compositions and structures of the complexes 1 a-5b have been determined by total elemental analyses, IR, 1H NMR, 13C NMR and mass spectra. The spectroscopic results indicate a substantial bond delocalization in the 1-aminoalkyne complexes 4a-4c and a hindered rotation of the diethylamino group in the alkyne ligand of 4c. The barrier to this rotation is calculated to be ca. 14.7 kcal/mol and compared with previously reported diethylaminoalkyne complexes. An X-ray crystallographic study of 5 b has been carried out. The compound crystallizes in the monoclinic space group P 21. The unit cell contains two molecules of 5 b, which have a distorted octahedral coordination geometry with a trans-arrangement of the bromo and the phenylcarbyne ligand. The four isocyanide ligands are slightly bent out of the equatorial plane towards the bromo ligand. Striking features of the structure are the shortest W=Ccarbyne and the longest W —Br bond lengths known for low valent tungsten aryl- and alkylcarbyne complexes indicating a high electron density at tungsten. In addition two isocyanide ligands show a bent geometry at nitrogen, which has been so far reported only for electron-rich isocyanide complexes.

Low-Valent Titanium-Mediated Radical Conjugate Addition Using Benzyl Alcohols as Benzyl Radical Sources

2018 ◽  
Vol 20 (17) ◽  
pp. 5389-5392 ◽  
Author(s):  
Takuya Suga ◽  
Shoma Shimazu ◽  
Yutaka Ukaji
Keyword(s):  
Conjugate Addition ◽  
Benzyl Alcohols ◽  
Benzyl Radical ◽  
Low Valent

Arene C–H Bond Coordination versus C–H Bond Cleavage in Low-Valent Group 6 Carbonyl Pincer Complexes

2016 ◽  
Vol 35 (17) ◽  
pp. 3032-3039 ◽  
Author(s):  
Sara R. M. M. de Aguiar ◽  
Berthold Stöger ◽  
Ernst Pittenauer ◽  
Günter Allmaier ◽  
Luis F. Veiros ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Pincer Complexes ◽  
Group 6 ◽  
Low Valent

Exploring Regioselective Bond Cleavage and Cross-Coupling Reactions using a Low-Valent Nickel Complex

2016 ◽  
Vol 22 (12) ◽  
pp. 4070-4077 ◽  
Author(s):  
Addison N. Desnoyer ◽  
Florian W. Friese ◽  
Weiling Chiu ◽  
Marcus W. Drover ◽  
Brian O. Patrick ◽  
...  
Keyword(s):  
Nickel Complex ◽  
Bond Cleavage ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Low Valent
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