2010
DOI: 10.1021/om900963p
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Metal-Free Frustrated Lewis Pair Catalyzed 1,4-Hydrogenation of Conjugated Metallocene Dienamines

Abstract: Frustrated Lewis pairs, highly active in heterolytic dihydrogen splitting, were used as active and very selective hydrogenation catalysts for organometallic substrates. Conjugated dienamines fixed at the ferrocene framework and at the zirconocene nucleus were selectively 1,4-hydrogenated under catalytic conditions at ambient temperature.

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Cited by 80 publications
(38 citation statements)
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“…[1,6] All of these reactions probably proceed by a reaction sequence characterized by initial protonation of the organic substrate followed by hydride transfer to the resulting reactive cationic species. [12] From this investigation and a related reaction studied by Soós et al, [13] there is now increasing evidence that FLP induced hydrogenation can also be carried out with a,bunsaturated carbonyl compounds. The FLP reduction of the activated carbon-carbon triple bonds probably follows a reversed sequence which is initiated by hydride addition to the b position of the substrate with subsequent protonation of the resulting boron-enolate intermediate (see Scheme 7).…”
Section: /Hmentioning
confidence: 68%
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“…[1,6] All of these reactions probably proceed by a reaction sequence characterized by initial protonation of the organic substrate followed by hydride transfer to the resulting reactive cationic species. [12] From this investigation and a related reaction studied by Soós et al, [13] there is now increasing evidence that FLP induced hydrogenation can also be carried out with a,bunsaturated carbonyl compounds. The FLP reduction of the activated carbon-carbon triple bonds probably follows a reversed sequence which is initiated by hydride addition to the b position of the substrate with subsequent protonation of the resulting boron-enolate intermediate (see Scheme 7).…”
Section: /Hmentioning
confidence: 68%
“…Again the cis-enone product is found initially, which can be explained by a reaction sequence of 1,4-hydridoborate addition to 3 e to give the allenic enolate intermediate (12) followed by preferred subsequent protonation by the very bulky tBu 3 PH + from the less hindered side (Scheme 5).…”
Section: /Hmentioning
confidence: 99%
“…Using 50 bar H 2 , 708C, and 10 mol % catalyst, the amine 101 e was isolated in over 80 % yield. [58] The salt 32, derived from heterolytic cleavage of H 2 by the frustrated Lewis pair 31/B(C 6 F 5 ) 3 , rapidly transfers proton and hydride stoichiometrically to the silyl enolether 102 a at room temperature. The reaction can also be carried out catalytically at 25 8C and 2 bar H 2 using 20 mol % of the 31/ B(C 6 F 5 ) 3 catalyst system.…”
Section: Frustrated Lewis Pairsmentioning
confidence: 99%
“…In contrast, the substrates 120 a,b are catalytically hydrogenated with 5 mol % of 27 a under H 2 to selectively yield the formal 1,4-hydrogenation products 121 a,b with only marginal amounts of the saturated products. [58,63] The iminium-ion intermediate of this catalytic metal-free hydrogenation was independently prepared by selective protonation of the dienamine 120 a with HCl in diethyl ether. [64] Subsequent anion exchange gave 123 [BF 4 ].…”
Section: Frustrated Lewis Pairsmentioning
confidence: 99%
“…Based on this observation, subsequent findings have led to the development of effective metal-free catalysts for the hydrogenation of imines, [2][3][4][5][6][7][8] aziridines, and protected nitriles. [2,3] Related alkyl-linked zwitterions, such as Mes 2 P(H)C 2 H 4 B(H)A C H T U N G T R E N N U N G (C 6 F 5 ) 2 , have also been discovered and shown to catalyze the hydrogenation of enamines, [4,9] silylenol ethers, [6] and selected N heterocycles. [10] In addition, new synthetic routes to such zwitterionic derivatives have been developed from the reactions of sterically encumbered frustrated Lewis pairs (FLPs) with a variety of small molecules including olefins, [11][12][13][14] alkynes, [15][16][17][18][19] CO 2 , [20][21][22] and N 2 O.…”
Section: Introductionmentioning
confidence: 99%