O-Methylarenehydroxamates as ortho-lithiation directing groups. Titanium(III)-mediated conversion of O-methyl hydroxamates to primary amides
摘要:
Reaction of O-methyl benzohydroxamates 2a-c with sec-butyllithium in the presence of TMEDA at -40-degrees-C regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g. 3). These dilithio species react avidly with a wide spectrum of electrophilic reagents, including alkyl halides, giving adducts which on reduction with TiCl3 are converted into ortho-substituted primary benzamides in excellent yields. Ortho lithiation of O-methyl benzohydroxamates is thus formally equivalent to ortho lithiation of primary benzamides themselves. The utility of these synthetic operations is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups. The conversion of 0-methyl hydroxamates to primary amides is shown to be general, as exemplified by transformation of 14a-f to 15a-f.O-Methyl 2-methylbenzohydroxamate (4a) undergoes regiospecific dilithiation on nitrogen and on the methyl group when treated with sec-butyllithium at -70-degrees-C. These dilithio species react with DMF or ''Weinreb-type'' amides to give condensation products which cyclize to N-methoxyisoquinolin-1(2H)-ones under mildly acidic conditions. Removal of the N-methoxy moiety under conditions analogous to those used for O-methyl benzohydroxamate provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency. This process is exemplified by the synthesis of isoquinolin-1(2H)-one 9a, its 3-n-butyl congener 9b, and the tricyclic isoquinolin-1 (2H)-ones 20a and 20b from O-methyl 2-methylbenzohydroxamate (4a).
Intermolecular Electrochemical C(<i>sp</i>
<sup>3</sup>
)-H/N-H Cross-coupling of Xanthenes with <i>N</i>
-alkoxyamides: Radical Pathway Mediated by Ferrocene as a Redox Catalyst
with xanthenes is reported. The protocol is carried out in an undivided cell under constant current conditions employing simple, cheap and readily available ferrocene (Fc) as a redox catalyst. Cyclic voltammetry and control experiments disclosed that the dehydrogenative cross‐coupling reaction may proceed via an amidyl radical.
The Rh(III)-catalyzed amidation of C(sp2)-H bonds has been reported by employing the N-methoxyamide as a novel amino source. An excellent level of functional group tolerance can be achieved when N-methoxyamide derivatives are used as the amidating reagents. Importantly, several known bioactive compounds such as Aminalon, Pregabalin, Gabapentin, and Probenecid can be transformed to effective amidating
derivatives were prepared by copper-catalyzedcross-coupling of hydroxamates with aryliodides. The reaction conditions are compatible with standard hydroxy-protecting groups on the hydroxylamine moiety and are applicable to a broad range of coupling partners. N-Aryl-O-alkylhydroxamic acid derivatives were prepared by copper-catalyzedcross-coupling of hydroxamates with aryliodides. The reaction conditions
Electrodimerization of <i>N</i>
-Alkoxyamides for Zinc(II) Catalyzed Phenolic Ester Synthesis under Mild Reaction Conditions
作者:Kripa Subramanian、Subhash L. Yedage、Bhalchandra M. Bhanage
DOI:10.1002/adsc.201701646
日期:2018.7.4
electrochemical On‐Off method for phenolic ester synthesis from N‐alkoxyamides has been reported. This one‐pot protocol begins with rapid and selective electrodimerization of the amide using n‐Bu4NI (TBAI) as an electrocatalyst. The reaction proceeds further in the absence of current via Zn catalyzed C−N bond activation of the amide dimer followed by its coupling with phenol to form the ester. The present
已经报道了从N-烷氧基酰胺合成酚酯的电化学开-关方法。这种一锅法的协议开始于使用n- Bu 4 NI(TBAI)作为电催化剂对酰胺进行快速和选择性的电二聚。在不存在电流的情况下,该反应会进一步通过酰胺催化的二聚体的Zn催化C-N键活化而进行,然后将其与苯酚偶联形成酯。本方法学不含配体,在温和的反应条件下进行。这种转变结合了多种酚和酰胺底物,导致形成功能化的酯,从而突出了其多功能性。
Copper‐Catalyzed Electrophilic Amidation of Organotrifluoroborates with Use of
<i>N</i>
‐Methoxyamides
A copper‐catalyzedelectrophilicamidation of aryltrifluoroborates with use of N‐methoxyamides is reported. The reaction shows high functional group compatibility derived from two distinct features: 1) the high stability of the N‐methoxyamides and 2) the nonbasic mild conditions in the presence of LiCl. The developed method can also be applied to the synthesis of enamides, which are widely distributed
据报道,使用N-甲氧基酰胺进行了铜催化的芳基三氟硼酸酯的亲电酰胺化反应。该反应显示出源自两个明显特征的高官能团相容性:1)N-甲氧基酰胺的高稳定性,以及2)在LiCl存在下的非碱性温和条件。所开发的方法还可以用于合成广泛分布于天然产物中的烯酰胺。初步的机理研究表明,第一步是在LiCl的协助下对三氟硼酸芳基酯进行金属转移,生成的芳基铜中间体通过非S N 2氧化添加至N-甲氧基酰胺并随后进行还原消除而提供了苯胺。