- Synthesis of trans-Configured Enol Ethers by a Sequence of syn-Selective Glycolate Aldol Addition, Hydrolysis, and Grob Fragmentation
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A trans-selective access to enol ethers with a disubstituted C=C bond was developed. It consists of a diastereoselective glycolate aldol addition, a hydrolysis, and a Grob fragmentation. Aldol additions of N-[(benzyloxy)acetyl]oxazolidinones furnished syn-aldols selectively. Hydrolytic removal of the auxiliaries gave α-benzyloxy-β-hydroxycarboxylic acids. Exposure to DMF dineopentylacetal induced Grob fragmentations, which delivered trans-configured enol ethers. Applying our 3-step sequence in a bidirectional synthesis led to bis(enol ethers) trans,trans-selectively, i.e., to a motif rarely encountered in the literature. A modified precursor synthesis allowed for the first time to access both the E- and the Z-isomer of an enol ether with a trisubstituted C=C bond stereoselectively using a Grob fragmentation route. The Ar–Br and C≡C–SiMe2tBu motifs of appropriate enol ethers engaged in follow-up reactions via organometallics. These provided more elaborated enol ethers.
- Engesser, Tobias,Brückner, Reinhard
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- Heck arylation of allyl alcohol catalyzed by Pd(0) nanoparticles
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Pd(0) nanoparticles ca. 2 nm in diameter were obtained by the reduction of PdCl2 and Pd(OAc)2 in water at 80 °C in the presence of a PVP-stabilizing polymer. Pd(0) NPs were successfully used in the Heck coupling of allyl alcohol with iodo- and bromobenzenes. Iodobenzenes reacted under solventless conditions or in DMF solution producing 3-arylpropanals and 2-arylpropanals as the main products. The same products were obtained in the reaction of bromobenzene in TBAB as the reaction medium. The stability of Pd(0) NPs was evidenced in recycling experiments. Similar Heck coupling results were also obtained with the palladium compounds PdCl2(cod) and Pd(OAc)2 under the same conditions.
- Tarnowicz, Stanis?awa,Alsalahi, Waleed,Mieczyńska, Ewa,Trzeciak, Anna M.
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p. 5605 - 5612
(2017/08/26)
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- Stereoselective organocatalytic oxidation of alcohols to enals: A homologation method to prepare polyenes
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A novel method for organocatalytic oxidation through oxidative enamine catalysis was developed with excellent compatibility for the direct syntheses of enals from simple saturated alcohols. By using this amine-catalyzed IBX-oxidation, a wide range of aromatic and aliphatic substituted enals were successfully generated in high yields and exclusively stereoselective E-geometry. Moreover, varying the solvents and/or the loading amounts of IBX allowed for the selective oxidation of alcohols and aldehydes. Importantly, the homologous application of this method provided a selective and efficient way of preparing various highly sensitive conjugated polyene frameworks, which are enriched in natural products.
- Chen, Xiaobei,Zhang, Yinan,Wan, Huixin,Wang, Wei,Zhang, Shilei
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p. 3532 - 3535
(2016/03/04)
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- Quaternary ammonium compounds having muscle relaxation activity
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A quaternary ammonium having a muscle relaxation activity compound represented by the formula (I): STR1 wherein R1 represents a methylene, a lower alkylenoxy, a lower alkenylene, a lower alkynylene, --CO--, --COO--, a lower alkylene carbonyloxy, --CH(OR5)--, a lower alkylenecarbonyl, a hydroxy lower alkylene, --O--, --S--, --SO--, or --SO2 --; R2 represents a hydrogen atom, a hydroxy lower alkyl, an aldehyde, a lower alkyl carbonyl, --NO2, or --NHR6 ; R3 represents a hydrogen atom of a group --R1 --(CH2)a --[CH(CH2 A)--CH2 ]b --A; R4 represents an anion; R5 and R6 represent a hydrogen atom or a acetyl; A represents a quaternary ammonium group; a represents an integer of 1 to 8; b represents 0 or 1; m represents an integer of 1 to 4; and (Z) represents a trivalent benzene ring, a trivalent naphthalene ring, a trivalent diphenyl or a trivalent ethane radical.
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