- Visible-light photocatalytic α-amino C(sp3)–H activation through radical translocation: a novel and metal-free approach to α-alkoxybenzamides
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Visible-light photocatalytic, metal-free synthesis of valuable α-alkoxybenzamides starting with readily prepared o-aminobenzamides and alcohols through radical translocation under mild conditions is reported. This protocol employs eosin Y as an organophot
- Huang, Feng-Qing,Dong, Xin,Qi, Lian-Wen,Zhang, Bo
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p. 1600 - 1604
(2018/03/22)
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- Exploratory synthetic studies of the α-methoxylation of amides via cuprous ion-promoted decomposition of o-diazobenzamides
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A convenient nonelectrochemical amide oxidation method has been developed. The process involves a cuprous ion-promoted decomposition of o-diazobenzamides like 4, generated in situ from the corresponding o-aminobenzamides, to give N-acyliminium ion intermediate 9 via a 1,5-H-atom transfer, followed by metal-catalyzed oxidation of the resulting α-amidyl radical. The transformation produces α-methoxybenzamides 15 in good yields. An attempt was made to apply this oxidation method to a total synthesis of the alkaloid (-)-anisomycin (16). Scalemic o-aminobenzamide pyrrolidine derivatives 18a/18b underwent oxidation to give α-methoxylated amide substrates 19a/19b, respectively, in good yields. However, alkylation of the N-acyliminium intermediate 20 with (p-methoxybenzyl)magnesium chloride gave the undesired anti-compounds 22a/22b as the major products. The amide oxidation exhibits good regioselectivity with many unsymmetrical 2-substituted piperidine and pyrrolidine systems. In general, it appears that the larger the C-2 substituent, the greater the methylene/methine H-atom abstraction ratio. A mechanistic rationale for this selectivity is suggested based upon amide rotamer populations. An extension of this methodology can be used to conduct two sequential amide oxidations using readily prepared 2-amino-6-nitrobenzamides such as 68 and 69.
- Han, Gyoonhee,LaPorte, Matthew G.,McIntosh, Mathias C.,Weinreb, Steven M.,Parvez, Masood
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p. 9483 - 9493
(2007/10/03)
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- A convenient synthetic method for amide oxidation
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Diazotization of o-aminobenzamides in methanol in the presence of a catalytic amount of CuCl affords α-methoxybenzamides in good yields.
- Han, Gyoonhee,McIntosh, Matthias C.,Weinreb, Steven M.
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p. 5813 - 5816
(2007/10/02)
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