30087-96-8Relevant academic research and scientific papers
Chemistry of Tertiary Carbon Center in the Formation of Congested C?O Ether Bonds
Hirata, Goki,Takeuchi, Kentarou,Shimoharai, Yusuke,Sumimoto, Michinori,Kaizawa, Hazuki,Nokami, Toshiki,Koike, Takashi,Abe, Manabu,Shirakawa, Eiji,Nishikata, Takashi
, p. 4329 - 4334 (2021)
Nucleophilic substitutions, including SN1 and SN2, are classical and reliable reactions, but a serious drawback is their intolerance for both bulky nucleophiles and chiral tertiary alkyl electrophiles for the synthesis of a chiral quaternary carbon center. An SRN1 reaction via a radical species is another conventional method used to carry out substitution reactions of bulky nucleophiles and alkyl halides, but chiral tertiary alkyl electrophiles cannot be used. Therefore, a stereospecific nucleophilic substitution reaction using chiral tertiary alkyl electrophiles and bulky nucleophiles has not yet been well studied. In this paper, we describe the reaction of tertiary alkyl alcohols and non-chiral or chiral α-bromocarboxamides as a tertiary alkyl source for the formation of congested ether compounds possessing two different tertiary alkyl groups on the oxygen atom with stereoretention.
Silver-Promoted Fluorination Reactions of α-Bromoamides
Mizuta, Satoshi,Kitamura, Kanami,Kitagawa, Ayako,Yamaguchi, Tomoko,Ishikawa, Takeshi
supporting information, p. 5930 - 5935 (2021/02/01)
Silver-promoted C?F bond formation in α-bromoamides by using AgF under mild conditions is reported. This simple method enables access to tertiary, secondary, and primary alkyl fluorides involving biomolecular scaffolds. This transformation is applicable to primary and secondary amides and shows broad functional-group tolerance. Kinetics experiments revealed that the reaction rate increased in the order of 3°>2°>1° α-carbon atom. In addition, it was found that the acidic amide proton plays an important role in accelerating the reaction. Mechanistic studies suggested generation of an aziridinone intermediate that undergoes subsequent nucleophilic addition to form the C?F bond with stereospecificity (i.e., retention of configuration). The synthesis of sterically hindered alcohols and ethers by using AgI is also demonstrated. Examples of reactions of α-bromoamides with O nucleophiles are presented.
Discovery of Oxygen α-Nucleophilic Addition to α,β-Unsaturated Amides Catalyzed by Redox-Neutral Organic Photoreductant
Luan, Zi-Hong,Qu, Jian-Ping,Kang, Yan-Biao
supporting information, p. 20942 - 20947 (2020/12/22)
The conjugate additions of oxygen-centered nucleophiles to conjugate acceptors are among the most powerful C-O bond formation reactions. The conjugate addition normally takes place at the β-position carbon to the electron-withdrawing group, resulting in the formation of a stabilized carbanion intermediate that can be quenched by proton or electrophiles to form the β-addition (i.e., hetero-Michael addition) products. On the contrary, the formation of α-hydroxyl or alkoxyl amides through conjugate addition needs an α,β-inverse addition. Nevertheless, a regio-inversed nucleophilic α-addition of oxygen-centered nucleophiles to α,β-unsaturated carbonyl compounds still remains less explored because of the electronic mismatch. In this research, we discovered the first α-specific nucleophilic addition of α,β-unsaturated amides with oxygen and fluoride nucleophiles. This region-inversed nucleophilic addition is enabled by the catalysis of a novel redox-neutral nondonor-acceptor organic photoreductant (CBZ6). As low as 0.5 mol % of visible light photoreductant was employed. The mechanistic insights were also explored. The oxidative potential of the excited state of CBZ6 is obtained in -1.92 V (vs SCE), presenting a stronger reductive potential than representative metal-cored or organic photoredox catalysts. This feature enabled the umpolung of α,β-unsaturated amides to take place α-nucleophilic addition other than the normal β-addition.
