Electroreductive Coupling of Phthalimides with α,β-Unsaturated Carbonyl Compounds and Subsequent Acid-Catalyzed Rearrangement to 4-Aminonaphthalen-1-ols: Density Functional Theory Study of the Acid-Catalyzed Rearrangement of Ketene Silyl Acetals

Abstract

The electroreductive coupling of phthalimides with α,β-unsaturated carbonyl compounds in the presence of TMSCl and successive treatment of the electrochemically coupled products with TFA gave two types of rearranged products, 3- and 2-substituted 4-aminonaphthalen-1-ols. The substituent (R) on the nitrogen atom of phthalimides determined which type of 4-aminonaphthalen-1-ol was preferentially formed. Bulky and less bulky N substituents selectively afforded 3- and 2-substituted 4-aminonaphthalen-1-ols, respectively. It was presumed by the density functional theory calculations for the acid-catalyzed rearrangement of silyl ketene acetals produced by the electroreductive coupling that the rearranged product selectivity depends on whether O or N protonation of the amide group of the silyl ketene acetals occurs more rapidly.

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

“…The second one is an anionic addition of an O-trimethylsilyl anion C, which is formed by a two-electron reduction of substrate 1 and O-trimethylsillylation, to 2a (path b). Unlike the two reactions previously reported by us that are presumed to proceed with the addition of an anion species (Scheme 1 and Scheme 2) [5,6], methyl acrylate (2c) is much less reactive as an acceptor in this reaction as shown in Scheme 6. The main product in this case was the same dimeric phthalide 9 as the product without the acceptor.…”

“…ry (Table 3) and acceptors 2 revealed no reduction peaks from 0 to −2.00 V vs SCE [5,6]. Therefore, this electroreductive coupling is initiated by the reduction of compounds 1.…”

“…Recently, we reported the electroreductive coupling of phthalic anhydrides with α,βunsaturated carbonyl compounds in the presence of chlorotrimethylsilane (TMSCl) and subsequent treatment with 1 M HCl to give 1,4-dihydroxynaphthalenes and 2-methyl-2,3-dihydronaphthalene-1,4-diones (Scheme 1) [5]. In addition, we disclosed that the electroreduction of phthalimides with α,βunsaturated carbonyl compounds under the same conditions and subsequent treatment with trifluoroacetic acid (TFA) produced 3-and 2-substituted 4-aminonaphthalen-1-ols (Scheme 2) [6]. In this context, we report here that the electroreduction of o-acylbenzoates 1 with acrylonitrile (2a) in the presence of TMSCl and subsequent treatment with 1 M HCl gives 2-cyanonaphthalen-1-ols 3 or 3-(3-cyanoethyl)phthalides 4 (Scheme 3).…”

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

“…ry (Table 3) and acceptors 2 revealed no reduction peaks from 0 to −2.00 V vs SCE [5,6]. Therefore, this electroreductive coupling is initiated by the reduction of compounds 1.…”

“…Recently, we reported the electroreductive coupling of phthalic anhydrides with α,βunsaturated carbonyl compounds in the presence of chlorotrimethylsilane (TMSCl) and subsequent treatment with 1 M HCl to give 1,4-dihydroxynaphthalenes and 2-methyl-2,3-dihydronaphthalene-1,4-diones (Scheme 1) [5]. In addition, we disclosed that the electroreduction of phthalimides with α,βunsaturated carbonyl compounds under the same conditions and subsequent treatment with trifluoroacetic acid (TFA) produced 3-and 2-substituted 4-aminonaphthalen-1-ols (Scheme 2) [6]. In this context, we report here that the electroreduction of o-acylbenzoates 1 with acrylonitrile (2a) in the presence of TMSCl and subsequent treatment with 1 M HCl gives 2-cyanonaphthalen-1-ols 3 or 3-(3-cyanoethyl)phthalides 4 (Scheme 3).…”