- High-value alcohols and higher-oxidation-state compounds by catalytic Z-selective cross-metathesis
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Olefin metathesis catalysts provide access to molecules that are indispensable to physicians and researchers in the life sciences. A persisting problem, however, is the dearth of chemical transformations that directly generate acyclic Z allylic alcohols, including products that contain a hindered neighbouring substituent or reactive functional units such as a phenol, an aldehyde, or a carboxylic acid. Here we present an electronically modified ruthenium-disulfide catalyst that is effective in generating such high-value compounds by cross-metathesis. The ruthenium complex is prepared from a commercially available precursor and an easily generated air-stable zinc catechothiolate. Transformations typically proceed with 5.0 mole per cent of the complex and an inexpensive reaction partner in 4-8 hours under ambient conditions; products are obtained in up to 80 per cent yield and 98:2 Z:E diastereoselectivity. The use of this catalyst is demonstrated in the synthesis of the naturally occurring anti-tumour agent neopeltolide and in a single-step stereoselective gram-scale conversion of a renewable feedstock (oleic acid) to an anti-fungal agent. In this conversion, the new catalyst promotes cross-metathesis more efficiently than the commonly used dichloro-ruthenium complexes, indicating that its utility may extend beyond Z-selective processes.
- Koh, Ming Joo,Khan, R. Kashif M.,Torker, Sebastian,Yu, Miao,Mikus, Malte S.,Hoveyda, Amir H.
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p. 181 - 186
(2015/03/30)
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- CATALYSTS FOR EFFICIENT Z-SELECTIVE METATHESIS
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The present application provides, among other things, compounds and methods for metathesis reactions. In some embodiments, provided compounds promote highly efficient and highly Z-selective metathesis. In some embodiments, provided compounds and methods are particularly useful for producing allyl alcohols. In some embodiments, provided compounds have the structure of formula I. In some embodiments, provided compounds comprise ruthenium, and a ligand bonded to ruthenium through a sulfur atom.
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Paragraph 00613-00614; 00641-00642
(2015/01/09)
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- Stille couplings in water at room temperature
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A nonionic amphiphile, TPGS-750-M, enables efficient Stille couplings between a wide range of substrates to be conducted in water as the only medium, in most cases at room temperature.
- Lu, Guo-Ping,Cai, Chun,Lipshutz, Bruce H.
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supporting information
p. 105 - 109
(2013/02/23)
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- Ligand effects on the stereochemistry of Stille couplings, as manifested in reactions of Z-alkenyl halides
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Unexpected losses in stereochemistry from Stille reactions involving Z-alkenyl halides have been shown to be ligand dependent. A new set of reaction conditions has been developed that, in most cases, leads to highly stereoselective cross-couplings under mild conditions, along with improved yields.
- Lu, Guo-Ping,Voigtritter, Karl R.,Cai, Chun,Lipshutz, Bruce H.
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supporting information; experimental part
p. 8661 - 8663
(2012/09/25)
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- Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation - Pd-catalyzed cross-coupling
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All four stereoisomers (7-10) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (E)- and (Z)-β-bromoacrylates. Although the stereoisomeric purity of the 2Z,4E-isomer (8) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤95%, as reported earlier, the use of CsF or nBu4NF as a promoter base has now been found to give all of 7-10 in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2E,4E and 2E,4Z isomers of ≥98% purity, but the purity of the 2Z,4E isomer was ≤95%. Mutually complementary Horner-Wadsworth-Emmons and Still-Gennari (SG) olefinations are also of considerably limited scopes. Neither 2E,4Z nor 2Z,4Z isomer is readily prepared in ≥90% selectivity. In addition to (2Z,4E)-dienoic esters, some (2Z,4E,6E)- and (2Z,4E,6Z)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation-SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (23-30) have been prepared in ≥98% overall selectivity.
- Wang, Guangwei,Mohan, Swathi,Negishi, Ei-Ichi
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p. 11344 - 11349
(2011/10/30)
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- Development of a method for the synthesis of α-substituted α,β- unsaturated lactones based on stille-type Pd-catalyzed carbonylation of (Z)- ω-iodoalkenols. An efficient and selective synthesis of (+)-hamabiwalactone B
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Pd-Catalyzed carbonylative lactonization of (Z)-ω-iodoalkenols can be applied to synthesize α/β-unsaturated lactones containing an alkenyl or alkynyl substituent in the α position, providing a generally superior alternative to recently developed methods involving Pd-catalyzed α- substitution of α-stannyl esters, as exemplified by a highly expeditious synthesis of (+)-hamabiwalactone B.
- Liao, Baiqiao,Negishi, Ei-Ichi
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p. 1241 - 1249
(2007/10/03)
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- Palladium-catalysed Reaction of Vinylic Halides with Allylic Alcohols: A Highly Chemo-, Regio- and Stereo-controlled Synthesis of Conjugated Dienols
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A new, direct, highly chemo-, regio- and stereo-controlled method for the construction of (E,E) and (E,Z) conjugated dienols from vinylic halides and allylic alcohols is described.
- Jeffery, Tuyet
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p. 324 - 325
(2007/10/02)
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- PALLADIUM-CATALYSED REACTION OF VINYLIC HALIDES WITH PRIMARY ALLYLIC ALCOHOLS: REGIO AND STEREOCONTROLLED SYNTHESIS OF 4-ENALS.
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Stereodefined γ,δ-unsaturated aldehydes can be prepared with high regio and stereocontrol by palladium-catalysed coupling of vinylic halides with primary allylic alcohols, in the presence of silver carbonate and tetra-n-butylammonium hydrogen sulphate.
- Jeffery, Tuyet
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p. 6641 - 6644
(2007/10/02)
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- Structural Dynamics of Pentadienyl Metal-Compounds Bearing a Terminal Alkyl Substituent: Both 'Stereoselective' and 'Stereodefensive' Synthesis of a Natural Perfume
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The (2Z,4E)-, (2E,4Z)- and (2E,4E)-isomers of 2,4-decandien-1-ol (5) have been obtained with high and predictable stereochemical homogeneity starting from both (Z)- and (E)-1,4-decadiene.These hydrocarbons were hydroxylated in a reaction sequence consisting of metallation (by means of s-butyllithium or butyllithium/potassium-t-butoxide, giving rise to organometallic intermediates of specific conformations), dimethoxyborylation and oxidation.The different decadienols as well as (2E,4Z)-2,4-undecadien-1-ol were converted into the isovalerates, the ester derived from (2E,4Z)-2,4-decadien-1-ol being a natural flavor component.
- Bosshardt, Herbert,Schlosser, Manfred
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p. 2393 - 2403
(2007/10/02)
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