- Scalable, Stereocontrolled Formal Syntheses of (+)-Isoschizandrin and (+)-Steganone: Development and Applications of Palladium(II)-Catalyzed Atroposelective C?H Alkynylation
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Dibenzocyclooctadiene lignans are an interesting class of molecules because of their unique structure based on an axially chiral biaryl moiety as well as their significant biological activity. Herein, we describe the development of a palladium-catalyzed atroposelective C?H alkynylation and its application in gram-scale, stereocontrolled formal syntheses of (+)-isoschizandrin and (+)-steganone. tert-Leucine was identified as an efficient, catalytic transient chiral auxiliary. A wide range of enantiomerically enriched biaryl compounds were prepared by this approach in good yields (up to 99 %) with excellent enantioselectivity (up to >99 % ee).
- Liao, Gang,Yao, Qi-Jun,Zhang, Zhuo-Zhuo,Wu, Yong-Jie,Huang, Dan-Ying,Shi, Bing-Feng
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supporting information
p. 3661 - 3665
(2018/03/05)
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- Pd-Catalyzed Atroposelective C?H Allylation through β-O Elimination: Diverse Synthesis of Axially Chiral Biaryls
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Biaryl atropisomers are of great importance in natural products, pharmaceuticals, and asymmteric synthesis. The efficient synthesis of these chiral scaffolds with full enantiocontrol and high diversity remains challenging. Reported herein is a Pd-catalyzed atroposelective C?H allylation with tert-leucine as an efficient catalytic chiral transient auxiliary. A wide range of enantioenriched biaryl aldehydes were prepared in synthetically useful yields with excellent enantioselectivity (up to >99 % ee) through β-O elimination. The reaction could be carried out on a gram scale without erosion of the ee value. A variety of axially chiral carboxylic acids could be obtained with high enantiopurity. The resulting axially chiral biaryl aldehydes and carboxylic acids might be used in asymmetric synthesis as chiral ligands and/or organocatalysts.
- Liao, Gang,Li, Bing,Chen, Hao-Ming,Yao, Qi-Jun,Xia, Yu-Nong,Luo, Jun,Shi, Bing-Feng
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supporting information
p. 17151 - 17155
(2018/12/04)
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- Microwave-assisted suzuki cross-coupling reaction, a key step in the synthesis of polycyclic aromatic hydrocarbons and their metabolites
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(Chemical Equation Presented) A highly efficient and general method for Suzuki cross-coupling reaction en route to the synthesis of polycyclic aromatic hydrocarbons (PAHs) and their metabolites has been developed. Microwave irradiation of aryl bromides 1
- Sharma, Arun K.,Gowdahalli, Krishnegowda,Krzeminski, Jacek,Amin, Shantu
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p. 8987 - 8989
(2008/03/12)
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- A New and Concise Synthesis of 3-Hydroxybenzo[c]phenanthrene and 12-Hydroxybenzo[g]chrysene, Useful Intermediates for the Synthesis of Fjord-Region Diol Epoxides of Benzo[c]phenanthrene and Benzo[g]chrysene
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A new strategy which involves a palladium-catalyzed cross-coupling reaction has been developed for the rapid synthesis of 3-hydroxybenzo[c]phenanthrene (5) and 12-hydroxybenzo[g]chrysene (6). These phenolic compounds are the key intermediates for the synthesis of highly carcinogenic fjord-region diol epoxide metabolites 3 and 4 of benzo[c]phenanthrene (1) and benzo[g]chrysene (2). The cross-coupling reaction of 2-bromo-5-methoxybenzaldehyde (9) with naphthalene-1-boronic acid (7) and phenanthrene-9-boronic acid (8) produced 2-(1-naphthyl)-5-methoxybenzaldehyde (10) and 2-(9-phenanthryl)-5-methoxybenzaldehyde (11), respectively, in quantitative yields. After reaction of these aldehydes with trimethylsulfonium iodide under phase-transfer conditions or with the Wittig reagent obtained from (methoxymethyl)triphenylphosphonium bromide and phenyllithium to generate an oxiranyl or methoxyethene side chain, the acid-catalyzed cyclization with methanesulfonic acid (or boron trifluoride) produced 3-methoxybenzo[c]phenanthrene (16) and 12-methoxybenzo[g]chrysene (17) in 61-64percent yields. Finally, demethylation of these methoxy derivatives 16 and 17 with boron tribromide resulted in the formation of the hydroxy analogues 5 and 6, respectively. The availability of this short and high-yielding regiospecific method for the synthesis of phenols 5 and 6 should allow the preparative-scale synthesis of the fjord-region diol epoxides 3 and 4. These diol epoxides are required as starting compounds for the synthesis of site-specifically modified oligonucleotides which are critically needed to elucidate the mechanism of carcinogenesis at the molecular level.
- Kumar, Subodh
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p. 8535 - 8539
(2007/10/03)
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