- A domino palladium-catalyzed C-C and C-O bonds formation via dual O-H bond activation: Synthesis of 6,6-dialkyl-6 H -benzo[ c ]chromenes
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An efficient Pd-catalyzed domino reaction of α,α-dialkyl-(2- bromoaryl)methanols to 6,6-dialkyl-6H-benzo[c]chromenes is presented. Their formation can be explained via a five membered Pd(II)-cycle that efficiently involves a domino homocoupling with the second molecule, β-carbon cleavage, and finally intramolecular Buchwald-Hartwig cyclization. This domino process effectively involves breaking of five σ-bonds (2C-Br, 2O-H, and a C-C) and formation of two new σ-bonds (C-C and C-O). This mechanistic pathway is unprecedented and further illustrates the power of transition metal catalysis.
- Mahendar, Lodi,Krishna, Jonnada,Gopi Krishna Reddy, Alavala,Venkat Ramulu, Bokka,Satyanarayana, Gedu
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supporting information; experimental part
p. 628 - 631
(2012/03/11)
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- Asymmetric synthesis of (S)-(-)-N-acetylcolchinol via Ullmann biaryl coupling
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A modified Ziegler Ullmann coupling process has been developed as the key step in an effective synthesis of (S)-(-)-N-acetylcolchinol, analogues of which are selective vascular targeting agents with potential importance in cancer chemotherapy. Asymmetric induction is achieved by enamide hydrogenation using FerroTANE catalysts.
- Broady, Simon D.,Golden, Michael D.,Leonard, John,Muir, James C.,Maudet, Mickael
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p. 4627 - 4630
(2008/02/06)
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- CHEMICAL PROCESSES FOR THE PREPARATION OF A COLCHINOL DERIVATIVE AND INTERMEDIATES
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A process for the preparation of a colchinol derivative of the Formula (I): wherein each R, which may be the same or different, is selected from (1-6C)alkyl, benzyl and C(O)(1-6C)alkyl, or two RO groups together form a (1-4C)alkylenedioxy group and Ac is acetyl, by reduction of the corresponding enamide of formula (II): Colchinol derivatives with high enantiomeric purity are obtained by hydrogenation in the presence of a transition metal catalyst, particularly a catalyst selected from a rhodium complex, a ruthenium complex or an iridium complex. Novel compounds of formula (II'): wherein each R, which may be the same or different, is selected from (1-6C)alkyl, benzyl and C(O)(1-6C)alkyl, or two RO groups together form a (1-4C)alkylenedioxy group, and P is hydrogen or a suitable hydroxy protecting group are also described.
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Page/Page column 34-35
(2008/06/13)
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- CHEMICAL PROCESSES AND INTERMEDIATES
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The present invention provides a process for the formation of an enamide (III) wherein each R is independently selected from (1-6C)alkyl, benzyl and C(O)(1-6C)alkyl, or two RO groups together form a (1-4C)alkylenedioxy group, comprising the steps of reductive acylation of an oxime of formula (IX) wherein each R is independently selected from (1-6C)alkyl, benzyl and C(O)(1-6C)alkyl, or two RO groups together form a (1-4C)alkylenedioxy group, and the hydroxy group may optionally be protected by a hydroxy protecting group; and thereafter if necessary, removal of any protecting groups. Intermediates to the enamide (III) and methods for their preparation are also described.
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Page/Page column 36; 37
(2008/06/13)
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- Formal Synthesis of the Antitumour Antibiotic CC-1065
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A formal total synthesis of the potent antitumour antibiotic CC-1065 (1) is described; both the cyclopropapyrroloindole (2) and the 'dimeric' pyrroloindole (3) are synthesized by routes involving vinyl azide chemistry.The cyclopropapyrroloindole (2) is prepared from 5-benzyloxy-2-bromoacetophenone (Schemes 3-5), the key steps being the formation of both indoles by decomposition of the azides (9) and (13).The dimer (3) is prepared by coupling the monomeric pyrroloindoles (25) and (27), followed by functional group transformations (Scheme 7).
- Bolton, Richard E.,Moody, Christopher J.,Pass, Martin,Rees, Charles W.,Tojo, Gabriel
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p. 2491 - 2500
(2007/10/02)
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