- Influence of Some Factors on the Progress of a New Reaction in the Chemistry of Organoaluminum Compounds
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Abstract: We earlier discovered a new reaction in the chemistry of organoaluminum compounds (OACs), specifically, the formation of O-isobutyl acetals on low-temperature (–70°C) treatment of seven-membered lactones with a double (or more) molar amount of diisobutylaluminum hydride (DIBAH) in methylene chloride. To assess the boundaries for the formation of isobutyl acetals depending on the ring size, we involved in the low-temperature hydride reduction six-, eight-, and thirteen-membered lactones. To determine how the scope of the new reaction depends on the nature of the organoaluminum reagent, we tested triisobutylaluminum (TIBA). To determine how the formation of isobutyl acetals on low-temperature (–70°C) reduction with excess DIBAH in CH2Cl2 depends on whether the starting ester is cyclic or acyclic and, if the former is the case, on the ring size in the ester, we used the acyclic methyl octadecanoate as the starting compound. It was found that the new reaction in the chemistry of AOC with DIBAH as the reducer is characteristic only of seven-membered lactones and atypical of acyclic methyl octadecanoate and ricinoleate (i.e. acids with the carbon chain length more than 6).
- Ishmuratov, G. Yu.,Vydrina, V. A.,Yakovleva, M. P.
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- Chemo- And regioselective hydroformylation of alkenes with CO2/H2over a bifunctional catalyst
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As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway.
- Hua, Kaimin,Liu, Xiaofang,Wei, Baiyin,Shao, Zilong,Deng, Yuchao,Zhong, Liangshu,Wang, Hui,Sun, Yuhan
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supporting information
p. 8040 - 8046
(2021/11/01)
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- Photoenzymatic Generation of Unstabilized Alkyl Radicals: An Asymmetric Reductive Cyclization
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Flavin-dependent "ene"-reductases can generate stabilized alkyl radicals when irradiated with visible light; however, they are not known to form unstabilized radicals. Here, we report an enantioselective radical cyclization using alkyl iodides as precursors to unstabilized nucleophilic radicals. Evidence suggests this species is accessed by photoexcitation of a charge-transfer complex that forms between flavin and substrate within the protein active site. Stereoselective delivery of a hydrogen atom from the flavin semiquinone to the prochiral radical formed after cyclization provides high levels of enantioselectivity across a variety of substrates. Overall, this transformation demonstrates that photoenzymatic catalysis can address long-standing selectivity challenges in the radical literature.
- Clayman, Phillip D.,Hyster, Todd K.
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supporting information
p. 15673 - 15677
(2020/10/18)
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- Comparison of “on water” and solventless procedures in the rhodium-catalyzed hydroformylation of diolefins, alkynes, and unsaturated alcohols
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Catalytic systems containing Rh(acac)(CO)2 or Rh/PAA (PAA?=?polyacrylic acid) and hydrophobic phosphine (PPh3) were used in the hydroformylation of diolefins, alkynes, and unsaturated alcohols under solventless and “on water” conditions. The total yield of dialdehydes obtained from 1,5-hexadiene and 1,7-octadiene reached 99%, and regioselectivity towards linear dialdehydes was higher in the “on water” system. The tandem hydroformylation-hydrogenation of phenylacetylene led to the formation of saturated aldehydes (3-phenylpropanal and 2-phenylpropanal) at 98% conversion with a good regioselectivity towards the linear aldehyde in the “on water” reaction. In contrast, solventless conditions appeared better in the hydroformylation of 1-propen-3-ol. 4-Hydroxybutanal, formed in this reaction with an excellent selectivity, was next transformed to tetrahydrofuran-2-ol via a ring-closure process. Cyclic products were also obtained in hydroformylation of 1-buten-3-ol. In reaction of undec-1-ol and 2-allylphenol linear aldehydes were formed with the yield 69–87%. The hydroformylation of 3-buten-1-ol performed under “on water” conditions showed very good regioselectivity towards a linear aldehyde, 5-hydroxypentanal. Further cyclization of the aldehyde to tetrahydropyran-2-ol was observed.
- Alsalahi,Trzeciak
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- First general methods toward aldehyde enolphosphates
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We herein report two innovative methods toward aldehyde enolphosphates and the first saccharidic aldehyde enolphosphates. Aldehyde enolphosphate function is worthwhile to be considered as a good phosphoenolpyruvate analogue.
- Barthes, Nicolas,Grison, Claude
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experimental part
p. 48 - 56
(2012/03/26)
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- Tandem rhodium-catalyzed hydroformylation-hydrogenation of alkenes by employing a cooperative ligand system
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Dual action: A multifunctional rhodium catalyst system enables the simultaneous catalysis of two distinct transformations, hydroformylation of an alkene and reduction of an aldehyde, in a highly selective manner. This one-pot/two-step process is controlled by the cooperative action of two different supramolecular ligand systems and transforms terminal alkenes into C1-chain-elongated linear alcohols. Copyright
- Fuchs, Daniela,Rousseau, Geraldine,Diab, Lisa,Gellrich, Urs,Breit, Bernhard
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supporting information; experimental part
p. 2178 - 2182
(2012/04/10)
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- Sunlight oxidation of alkyl aryl tellurides to the corresponding carbonyl compounds: A new carbonyl precursor
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Alkyl aryl tellurides were efficiently transformed to the corresponding carbonyl compounds by photo-oxidation with sunlight without affecting various functional groups in the alkyl moiety. The tellurides can be used as a new carbonyl precursor, and the photolysis can be conducted without special equipment for light sources.
- Ouchi, Akihiko,Hyugano, Takeshi,Liu, Chuanxiang
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supporting information; experimental part
p. 4870 - 4873
(2010/01/06)
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- Chemoenzymatic synthesis of ferrulactone II and (2E)-9-hydroxydecenoic acid
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A novel and divergent synthesis of the title compounds has been developed. The salient features of the synthesis were use of easily accessible starting material, regioselective organometallic reaction and enzymatic derivation of the key synthons.
- Pawar,Sankaranarayanan,Chattopadhyay
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p. 2219 - 2226
(2007/10/03)
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