- Partial reduction of annulated heterocycles as a general route to medium rings containing oxygen and nitrogen.
-
The preparation of annulated furans and pyrroles is described as part of a general strategy for the synthesis of medium ring heterocycles. After Birch reduction, the corresponding dihydro compounds were oxidatively cleaved to produce medium ring ethers an
- Donohoe,Raoof,Linney,Helliwell
-
-
Read Online
- The Quinary Catalyst-Substrate Complex Induced Construction of Spiro-Bridged or Cagelike Polyheterocyclic Compounds via a Substrate-Controlled Cascade Process
-
The asymmetric organocatalytic cascade reaction of cyclic β-oxo aldehydes to 2-hydroxycinnamaldehydes is developed. The bifunctional tertiary amine-thiourea catalyst was used in a rationally designed multiple catalysis where the asymmetric iminium catalysis and thiourea anion-binding catalysis were combined by carboxylate anion as a ternary catalytic system to form a quinary catalyst-substrate complex, providing an efficient protocol for the construction of enantioenriched spiro-bridged or cagelike polyheterocyclic compounds. The reuse of catalysts was also successfully realized.
- Wang, Chen,Chen, Ying-Han,Wu, Hui-Chun,Wang, Cong,Liu, Yan-Kai
-
-
Read Online
- Accessible, highly active single-component β-ketiminato neutral nickel(II) catalysts for ethylene polymerization
-
A series of novel neutral nickel complexes based on cyclic β-ketiminato ligands, [(2,6-iPr2C6H 3)N - CHC6H8O]Ni(Ph)(PPh3) (3b), [(2,6-iPr2C6H3)N - CHC n+3H2n+2O(C6H4)]Ni(Ph)(PPh 3) (6a-c), and [(2,6-iPr2C6H 3)N - CHCn+3H2n+2O(C6H 4)]Ni(CH3)(Py) (7a-c: a, n = 0; b, n = 1; c, n = 2) have been synthesized and characterized. These conveniently accessible complexes proved to be highly active catalysts for ethylene polymerization without an activator. Under the optimized conditions, an activity of 71.4 kg of PE/((mol of Ni) h atm) was observed using 6c as a catalyst. Particularly, it is of great interest that a bulky substituent proximate to the oxygen atom of the β-ketiminato complex is no longer a prerequisite to attain high catalytic efficiency, which is much different from the case for salicylaldiminato neutral nickel catalysts. This is effectively supported by the lower activation enthalpy changes of complexes 3b and 6a-c relative to values for the classic salicylaldiminato complexes. Moreover, for complexes 6a-c and 7a-c, the degree of conjugation between the phenylene ring and the corresponding nickel chelate of the complex can be tuned via changes in the ligand structure, which remarkably influence the molecular weights and the microstructures of the resulting polyethylenes. In comparison with the highly conjugated complexes 6a and 7a, complexes 6b,c and 7b,c, with a low degree of conjugation, produced polyethylenes with much higher molecular weights and lower branch contents. X-ray crystallographic analysis of 3b and 6a-c provides detailed information about the differences among these structures, and various typical angles and bond distances produce evidence of the conjugation modulation effect.
- Song, Dong-Po,Wu, Ji-Qian,Ye, Wei-Ping,Mu, Hong-Liang,Li, Yue-Sheng
-
-
Read Online
- Total Synthesis of Marine Alkaloid Hyellazole and its Derivatives
-
The total synthesis of the naturally occurring marine alkaloids hyellazole and chlorohyellazole was attempted from the corresponding easily accessible 2-methyl-1-ketotetrahydrocarbazoles obtained through the Japp–Klingemann reaction, followed by Fischer indole cyclization and subsequent Grignard coupling with phenylmagnesium bromide. Grignard coupling with 2-methyl-1-ketotetrahydrocarbazole unfortunately led directly to 2-methyl-1-phenylcarbazole through dehydration followed by aromatization through aerial oxidation, but application of the same reaction conditions to 6-chloro-2-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one, with careful treatment, led to the isolation of 6-chloro-2-methyl-1-phenyl-4,9-dihydro-3H-carbazole. However, selenium dioxide oxidation of this dihydrochloro derivative led to the formation of 6-chloro-2-methyl-1-phenyl-9H-carbazole. A different route was then adopted: a suitably substituted aromatic amine was used to establish the substitution pattern of the required carbazole derivative with a bromo group at C-1, and the required phenyl group at the 1-postion was then attached through Suzuki–Miyaura cross-coupling to furnish hyellazole.
- Chakraborty, Suchandra,Saha, Chandan
-
p. 2013 - 2021
(2018/05/15)
-
- Total synthesis of (+)-cyperolone
-
The total synthesis of (+)-cyperolone, an eudesmane-derived sesquiterpenoid from Cyperus rotundus, is described. The de novo synthesis was accomplished via a 15 step sequence starting from (R)-(-)-carvone. The synthetic route features a platinum-catalyzed
- Klahn, Philipp,Duschek, Alexander,Liebert, Clemence,Kirsch, Stefan F.
-
supporting information; experimental part
p. 1250 - 1253
(2012/05/19)
-
- Anti-Cytokine Heterocyclic Compounds
-
Heterocyclic compounds and analogues thereof and their use as inhibitors of Mitogen-Activated Protein Kinase-Activated Protein kinase-2 (MAPKAP-k2), and also to a method for preventing or treating a disease or disorder that can be treated or prevented by
- -
-
Page/Page column 50-51
(2010/11/25)
-
- THE PREPARATION β-KETOALDEHYDES
-
β-Ketoaldehydes(7) were prepared by the addition of bromophenylthiotrimethylsilylmethane(6) to trimethylsilyl enol ethers(3) followed by a sila-Pummerer rearrangement and hydrolysis.
- Ager, David J.
-
p. 419 - 422
(2007/10/02)
-
- REGIOSPECIFIC SYNTHESIS OF α-(PHENYLTHIO)CYCLOALKENONES AND OF α-PHENYL-α-(PHENYLTHIO)KETONES VIA αα-ADDITION OF PHENYLSULPHENYL CHLORIDE TO α-DIAZOKETONES
-
Cyclic α-diazoketones react with phenylsulphenyl chloride at room temperature to furnish α-chloro-α-(phenylthio)cycloalkanones which undergo ready dehydrochlorination to α-(phenylthio)cycloalkenones when treated with triethylamine; acyclic, terminal α-diazoketones also furnish α-chloro-α-(phenylthio)adducts which are useful electrophiles in the synthesis of α-phenyl-α-(phenylthio)ketones.
- McKervey, M. Anthony,Ratananukul, Piniti
-
p. 117 - 120
(2007/10/02)
-