- Nickel-Catalyzed Conversion of Enol Triflates into Alkenyl Halides
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A Ni-catalyzed halogenation of enol triflates was developed and it enables the synthesis of a broad range of alkenyl iodides, bromides, and chlorides under mild reaction conditions. The reaction utilizes inexpensive, bench-stable Ni(OAc)2?4 H2O as a precatalyst and proceeds at room temperature in the presence of sub-stoichiometric Zn and either 1,5-cyclooctadiene or 4-(N,N-dimethylamino)pyridine.
- Hofstra, Julie L.,Poremba, Kelsey E.,Shimozono, Alex M.,Reisman, Sarah E.
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supporting information
p. 14901 - 14905
(2019/11/11)
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- Nickel-catalyzed carboxylation of aryl and vinyl chlorides employing carbon dioxide
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Nickel-catalyzed carboxylation of aryl and vinyl chlorides employing carbon dioxide has been developed. The reactions proceeded under a CO2 pressure of 1 atm at room temperature in the presence of nickel catalysts and Mn powder as a reducing agent. Various aryl chlorides could be converted to the corresponding carboxylic acid in good to high yields. Furthermore, vinyl chlorides were successfully carboxylated with CO2. Mechanistic study suggests that Ni(I) species is involved in the catalytic cycle.
- Fujihara, Tetsuaki,Nogi, Keisuke,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 9106 - 9109
(2012/07/13)
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- The 2-Chloro-3-indenylmethyloxycarbonyl and Benzinden-3-ylmethyloxycarbonyl Base-Sensitive Amino-Protecting Groups. Application to an Inverse Merrifield Approach to Peptide Synthesis
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Two new base-labile amino-protecting groups, which are more sensitive than the FMOC function, are described: the 2-chloro-3-indenylmethyloxycarbonyl (CLIMOC) and benzinden-3-ylmethyloxycarbonyl (BIMOC) groups.The former was determined to be usable in solvents such as methylene dichloride but not in DMF, the latter in any common solvent including DMF.Key intermediate alcohols 10 and 16 were synthesized from 2-chloroindene (9) and benzindene (14).Treatment of indene with chlorine gave 8, which upon dehydrochlorination with DMF gave 9, which was then converted to 10 by standard procedure involving formylation and reduction.Benzindene was converted to its anion by means of n-butyllithium and the anion hydroxymethylated by gaseous formaldehyde.The alcohols were converted to the corresponding chloroformates and thence to succinimido ester 12 and azidoformate 18 for clean, selective protection of amino acids.Model CLIMOC- and BIMOC-amino acids were synthesized and demonstrated to be useful in carrying out a continous peptide synthesis via a two-polymer (polymeric reagents) approach.The protected amino acids were first loaded onto a phenolic polymer such as 21, and the resulting polymeric active esters were used to acylate an amino acid ester or peptide ester.The resulting protected peptide esters were deblocked via silica-based reagents 6 or 23.The acylation step was then repeated with the next amino acid, and the synthesis continued in the same way until completed.Tetrapeptide 26 and pentapeptide 27 were synthesized in this way via CLIMOC (CH2Cl2) and BIMOC (DMF) protection, respectively.These represent the first examples of clean, continous two-polymer syntheses carried out in a single solvent without the release of any low molecular weight byproducts into the solution. the fi
- Carpino, Louis A.,Cohen, Beri J.,Lin, Yao-Zhong,Stephens, Kenton E.,Triolo, Salvatore
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p. 251 - 259
(2007/10/02)
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- Generation of 2-Chloronaphthalene-1,3-diyl
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Reaction of 1-bromo-3,4-benzo-6,6-dichlorobicyclohexane with potassium tert-butoxide in tetrahydrofuran yields 2-chloronaphthalene along with nine other naphthalenes which result from solvent incorporation or reaction with nucleophile (Br-, Cl-, t-BuO-).Use of tetrahydrofuran-d8 as the solvent leads to the incorporation of two deuterium atoms into the chloronaphthalene.This result is interpreted in terms of a 1,3-dehydronaphthalene opening to the diradical, followed by abstraction of deuterium atoms from the solvent.The products which result from incorporation of solvent would then arise by dimerization of radical pairs.The remaining products are thought to arise from nucleophilic addition to the closed form of the dehydronaphthalene.
- Billups, W.E.,Buynak, John D.,Butler, Dorothy
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p. 4636 - 4641
(2007/10/02)
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