Ruthenium-catalyzed regioselective α-alkylation of ketones with primary alcohols

Cho, Chan Sik; Kim, Bok Tae; Kim, Tae‐Jeong; Shim, Sang Chul

doi:10.1016/s0040-4039(02)01625-8

Cited by 171 publications

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“…We previously reported that a hydrogen acceptor triggers the increase of reactivity and selectivity in the ruthenium-catalyzed coupling between ketones (or secondary alcohols) and primary alcohols. 5,8 However, as can be seen from entry 5, the selectivity of 3a/4 was not affected by the presence of the hydrogen acceptor and the yield of 4 showed no significant change.Given these results, the reactions between 1 and various ketones 2 were screened in order to synthesize a wide range of β-ferrocenylketones 3 (Table 2). Alkyl aryl ketones (2a-2j) were readily reacted with 1 to give the corresponding β-ferrocenylketones (3a-3j) in the range of 20-77% yields.…”

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confidence: 87%

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confidence: 87%

“…Similar regioselectivity was observed by others 12 and in our recent reports. 4,5,8,13 A possible reaction pathway based on our recent reports, 4,8 …”

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confidence: 99%

“…1 During the course of our ongoing studies on ruthenium-catalyzed organic syntheses and transformations, we recently found an unusual type of ruthenium-catalyzed transfer hydrogenation 2,3 of ketones by primary alcohols accompanied by C-C coupling. 4,5 The preferential formation of coupled secondary alcohols C to coupled ketones D was attributed to the use of an excess amount of alcohols B to ketones A ([B]/[A] = 3) (Scheme 1, route a). 4 Thus, when equimolar amounts of both substrates ([B]/[A] = 1) were used under similar ruthenium catalyst system, α-alkylated ketones D were preferentially formed (Scheme 1, route b).…”

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“…4 Thus, when equimolar amounts of both substrates ([B]/[A] = 1) were used under similar ruthenium catalyst system, α-alkylated ketones D were preferentially formed (Scheme 1, route b). [5][6][7] In addition, we recently disclosed an unprecedented ruthenium-catalyzed coupling between secondary alcohols E and primary alcohols B which leads to secondary alcohols C (Scheme 1, route c). 8 Prompted by these findings, 9 we have directed our attention to the extension of this alkylation (Scheme 1, route b).…”

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An Efficient Direct Synthesis of β-Ferrocenylketones Catalyzed by Ruthenium

2004

Bulletin of the Korean Chemical Society

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Transition metal-catalyzed carbon-carbon bond forming reaction has been widely used as a fundamental synthetic tool in organic synthesis.1 During the course of our ongoing studies on ruthenium-catalyzed organic syntheses and transformations, we recently found an unusual type of ruthenium-catalyzed transfer hydrogenation 2,3 of ketones by primary alcohols accompanied by C-C coupling.4,5 The preferential formation of coupled secondary alcohols C to coupled ketones D was attributed to the use of an excess amount of alcohols B to ketones A ([B]/[A] = 3) (Scheme 1, route a). 4 Thus, when equimolar amounts of both substrates ([B]/[A] = 1) were used under similar ruthenium catalyst system, α-alkylated ketones D were preferentially formed (Scheme 1, route b). [5][6][7] In addition, we recently disclosed an unprecedented ruthenium-catalyzed coupling between secondary alcohols E and primary alcohols B which leads to secondary alcohols C (Scheme 1, route c).8 Prompted by these findings, 9 we have directed our attention to the extension of this alkylation (Scheme 1, route b). Herein we report a ruthenium-catalyzed efficient direct synthesis of β-ferrocenylketones from ferrocenemethanol and ketones. 10 The results of several attempted couplings between ferrocenemethanol (1) and acetophenone (2a) are listed in Table 1. Treatment of equimolar amounts of 1 and 2a in dioxane in the presence of RuCl 2 (PPh 3 ) 3 (5 mol%) and KOH (3 equiv) at 80 o C for 24 h afforded 3-ferrocenyl-1-phenylpropan-1-one (3a) in 58% isolated yield with concomitant formation of 3-ferrocenyl-1-phenylpropenone (4, 14%) (entry 1).11 When the reaction was carried out at room temperature, 3a was obtained in only 30% yield even for a longer reaction time (43 h ) showed no significant change (entries 3 and 4). We previously reported that a hydrogen acceptor triggers the increase of reactivity and selectivity in the ruthenium-catalyzed coupling between ketones (or secondary alcohols) and primary alcohols. 5,8 However, as can be seen from entry 5, the selectivity of 3a/4 was not affected by the presence of the hydrogen acceptor and the yield of 4 showed no significant change.Given these results, the reactions between 1 and various ketones 2 were screened in order to synthesize a wide range of β-ferrocenylketones 3 (Table 2). Alkyl aryl ketones (2a-2j) were readily reacted with 1 to give the corresponding β-ferrocenylketones (3a-3j) in the range of 20-77% yields. The yield of 3 was affected by the position and electronic nature of the substituent on the aromatic ring of the ketones 2a-2j.With meta-and para-substituted ketones, the product yield was higher than that with ortho-substituted ketones (2b, 2e and 2g). With ketones (2h and 2i) having electron-withdrawing substituents such as 4-fluoro and 3-trifluoromethyl, the product yield was lower than that when ketones having electron-donating substituents such as methyl and methoxy were employed. In cases of dialkyl ketones (2k-2m), the alkylation took place exclusively at the less-hindered methyl position over α-...

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confidence: 87%

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confidence: 87%

“…Similar regioselectivity was observed by others 12 and in our recent reports. 4,5,8,13 A possible reaction pathway based on our recent reports, 4,8 …”

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confidence: 99%

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confidence: 99%

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confidence: 99%

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