Stereoselective Cross-Coupling of Benzylic Bromides and Vinyl Stannanes

Kamlage, Stefan; Sefkow, Michael; Peter, Martin G.

doi:10.1021/jo981840n

Cited by 30 publications

(12 citation statements)

References 14 publications

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“…A series of substituted butenediols, 6a-g, were synthesised according to an earlier reported procedure. 14 These compounds were subsequently hydrogenated in presence of chiral catalysts (Scheme 4 and Table 2). Diol 6a was reduced under different conditions, varying the catalyst and the catalyst loading (Table 2, entries 1-6).…”

Section: Scheme 3 New Strategy For the Preparation Of Optically Active Lactonesmentioning

confidence: 99%

Concise Synthesis of (+)-β-Benzyl γ-Butyrolactones from Butynediol

Kamlage¹,

Sefkow²,

Zimmermann³

et al. 2002

Synlett

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The synthesis of optically active b-benzyl-g-butyrolactones from butynediol via four transition metal catalysed reactions is reported. Key reactions are the hitherto unknown enantioselective hydrogenation of 2-benzyl-2-buten-1,4-diols using Ir(I)-phosphinooxazoline catalysts and the regiocontrolled oxidation of the resulting 2-benzyl-1,4-butanediols to the b-substituted butyrolactones.Key words: (+)-b-benzyl g-butyrolactones, butynediol, enantioselective hydrogenation Butyrolactone lignans 1 3 are an important class of natural products possessing notable biological activities, in particular antiviral, 4 cytotoxic 5 and canceroprotective 6 properties. We have recently reported a short synthesis of racemic butyrolactone lignans 1 via a-alkylation of b-substituted butyrolactones 2 (Scheme 1). 7 These lactone intermediates were prepared by Raney-Nickel or Pd/C catalysed hydrogenation of the corresponding unsaturated lactones 3, which were obtained from butynediol 4 in three transition metal catalysed reactions. 7 Scheme 1 Retrosynthesis of lactone lignans 1Since natural lignans 1 are generally non-racemic, an asymmetric hydrogenation of 3a-d to 2a-d using chiral catalysts was envisioned to provide optically active lignans and analogs (Scheme 2). Transition metal catalysed asymmetric hydrogenation of b-or g-methylene butyrolactones have been described. 8 However, we observed that butenolides 3a-d gave poor conversions upon homogeneous hydrogenation in the presence of chiral catalysts (Table 1). Thus, butenolides 3a,b were converted to lactones 2a,b in about 20% and 12% ee (2 h, 100 bar H 2 ) using Ir(I)-phosphinooxazoline catalyst A 9 (Table 1, entries 1 and 3). The conversion was 58% after 18 hours while the ee remaining low at 12% (entry 2). Similarly, reduction of 3b or 3d in presence of R-(+)-BINAP-Ru(II) 10 (120 h, 20-30 bar) afforded lactones 2b and 2d in 55 and 95% conversion, again with low ee (entries 4 and 5). 11It was reported that yeast reduction of butenolides afforded the corresponding lactones with good ee. 12 In our case, substrate 3c was reduced by yeast in the presence 12 or in the absence 13 of saccharose. The conversion of 3c to lactone 2c was 20% in each instance and the product was obtained as a racemic mixture (entries 6 and 7). Scheme 2 Attempted enantioselective reductions of lactones 3a-dSince neither asymmetric hydrogenation nor yeast reduction gave lactones 2 in acceptable yields and enantioselectivities, a different synthetic strategy was necessary. Thus, lactones 2 should be obtained by regioselective TPAP oxidation of optically active diols 5, prepared by asymmetric hydrogenation of butenediols 6 (Scheme 3).Scheme 3 New strategy for the preparation of optically active lactones 2

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Section: Scheme 3 New Strategy For the Preparation Of Optically Active Lactonesmentioning

confidence: 99%

Concise Synthesis of (+)-β-Benzyl γ-Butyrolactones from Butynediol

Kamlage¹,

Sefkow²,

Zimmermann³

et al. 2002

Synlett

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“…[11] A number of catalyst systems have been developed in the laboratories of Flaherty, [12] Kuwano, [13] Molander [9] and others. [23][24][25][26][27][28][29][30][31][32][33] Palladacycles are one class of the fascinating organometallic reagents and efficient catalysts for constructing carbon-carbon bonds. Inferior tolerance of functional groups, use of toxic reagents and longer reaction times are the disadvantages associated with some of the reported methods involving Suzuki cross-coupling reaction.…”

Section: Introductionmentioning

confidence: 99%

Cyclopalladated ferrocenylimine as an efficient catalyst for the syntheses of diarylmethane derivatives

Peng

et al. 2012

Applied Organom Chemis

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The cyclopalladated ferrocenylimine adducts Ia-c were evaluated in the Suzuki cross-coupling reaction of benzyl halides with arylboronic acids. The tricyclohexylphosphine adduct Ia exhibited highly catalytic activity for the coupling of aryl and heteroaryl boronic acids containing various functional groups with benzylic bromides and chlorides (up to 99% yield), furnishing diarylmethane derivatives with low catalyst loading (1 mol%). It is worth noting that catalyst Ia can be reused eight times without losing its catalytic activity.

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“…4 There are other instances in which Pd(0)-catalysed couplings of benzylic halides under Stille-type conditions have been reported. 5 Other Suzuki coupling reactions of benzyl halides have been described. [6][7][8][9][10][11][12][13][14][15] Several non-traditional methods have been developed for the Suzuki-Miyaura synthesis of unsymmetrical biaryls such as high intensity ultrasound [16][17] and especially microwave irradiation, [18][19][20][21][22] which also promotes the reaction of aryl chlorides and acid chlorides.…”

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confidence: 99%