- Bidentate auxiliary-directed alkenyl C-H allylation: Via exo-palladacycles: Synthesis of branched 1,4-dienes
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An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-Alkenes and allyl carbonates. With the use of an 8-Aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-Assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
- Shen, Cong,Lu, Xiunan,Zhang, Jian,Ding, Liyuan,Sun, Yaling,Zhong, Guofu
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supporting information
p. 13582 - 13585
(2019/11/14)
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- Alkenyl Carbonyl Derivatives in Enantioselective Redox Relay Heck Reactions: Accessing α,β-Unsaturated Systems
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A highly enantioselective and site-selective Pd-catalyzed arylation of alkenes linked to carbonyl derivatives to yield α,β-unsaturated systems is reported. The high site selectivity is attributed to both a solvent effect and the polarized nature of the carbonyl group, both of which have been analyzed through multidimensional analysis tools. The reaction can be performed in an iterative fashion allowing for a diastereoselective installation of two aryl groups along an alkyl chain.
- Zhang, Chun,Santiago, Celine B.,Kou, Lei,Sigman, Matthew S.
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p. 7290 - 7293
(2015/06/30)
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- Composition of the cloacal gland secretion of tuatara, Sphenodon punctatus
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The lipophilic content of the cloacal gland secretion of the tuatara (Sphenodon punctatus) was investigated. GC/EI-MS Analysis of CH2Cl2 extracts of the secretions revealed triacylglycerols as major glandular constituents. Twelve major medium-chain fatty acids were found to be conjugated to glycerol in different combinations, resulting in complex mixtures. These acids were identified by transesterification and subsequent derivatization of natural samples, and their structures were verified by synthesis. The natural glycerides contain predominantly three of the following acids: octanoic (A), (E)- and (Z)-oct-4-enoic (B and C, resp.), (4E,6Z)-octa-4,6-dienoic (tuataric acid;D), (R)-2,6-dimethylheptanoic (E), (R)-2,6-dimethylhept-5-enoic (F), (Z)-dec-4-enoic (G), (4Z,7Z)-deca-4,7-dienoic (H), (R)-3,7-dimethyloct-6-enoic (I), (R)-4,8-dimethylnon-7-enoic (J), (2R,6S)-2,6,10-trimethylundec-9-enoic (K), and (2R,5E)-2,6,10-trimethylundeca-5,9-dienoic acids (L). Several additional acids, occurring in trace amounts only, were tentatively identified by MS. The elucidation of the absolute configuration of the acids was performed by GC on chiral phases. Individual tuatara show specific mixtures of glycerides with up to 100 components. The individual mixtures may permit individual recognition because the bouquets seem to be stable over years.
- Flachsbarth, Birte,Fritzsche, Matthias,Weldon, Paul J.,Schulz, Stefan
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experimental part
p. 1 - 37
(2010/04/23)
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- Defense Mechanisms of Arthropods. 83. α- and β-Necrodol, Novel Terpenes from a Carrion Beetle (Necrodes surinamensis, Silphidae, Coleoptera)
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The defensive secretion obtained from the rectal gland of the carrion beetle Necrodes surinamensis has been found to consist of a mixture of aliphatic acids and terpene alcohols.Octanoic acid, decanoic acid, (Z)-3-decenoic acid, (Z)-4-decenoic acid, hexadecanoic acid, and octadecanoic acid are the chief acidic components.The three major terpenes are lavandulol and α- and β-necrodol.The necrodols were shown to have a 1,2,2,3,4-pentamethylcyclopentane framework not previously found among natural monoterpenes.Formulas 9 and 10 are derived for α- and β-necrodol, respectively, chiefly on the basis of mass spectrometric and NMR spectroscopic analysis.
- Roach, Braden,Eisner, Thomas,Meinwald, Jerrold
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p. 4047 - 4051
(2007/10/02)
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