The Behavior of 1,<i>n</i>-Enynes in the Presence of Transition Metals

Aubert, Corinne; Buisine, Olivier; Malacrìa, Max

doi:10.1021/cr980054f

Cited by 931 publications

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“…The dicationic [(MeCN) 4 Pd](BF 4 ) 2 complex (34 -37) in DMSO was found to be catalytically more active, affording 19% of (E)-2a and 61% of (E)-3a at lower temperatures (entry 2). The (E)-olefin geometries of cyclized products 2a and 3a…”

Section: Resultsmentioning

confidence: 99%

“…The Pd(II)-catalyzed cyclization of enyne 1a took place with 5 mol% of [(MeCN) 4 Pd](BF 4 ) 2 or Pd(OCOCF 3 ) 2 and 5.5 mol% of diphosphine ligands such as (R)-BINAP in well deaerated DMSO or benzene, respectively, to afford the six-membered cyclization products 2a and 3a (type D) in good yields ( Table 1). The dicationic [(MeCN) 4 Pd](BF 4 ) 2 complex (34 -37) in DMSO was found to be catalytically more active, affording 19% of (E)-2a and 61% of (E)-3a at lower temperatures (entry 2).…”

Section: Resultsmentioning

confidence: 99%

“…Analytical TLC was performed on glass plates (Merck Kieselgal 60 F 254 ; layer thickness, 0.25 and 0.2 mm). Visualization was accomplished by UV light (254 nm), anisaldehyde, KMnO 4 , and phosphomolybdic acid. Column chromatography was performed on Kanto Silica Gel 60N (spherical, neutral; Kanto Kagaku, Tokyo).…”

Section: Methodsmentioning

confidence: 99%

“…To a Pyrex test tube well degassed DMSO (2.0 ml) was injected, and argon was charged. [(MeCN) 4 Pd](BF 4 ) 2 (11.1 mg, 0.025 mmol) and (R)-BINAP (17.1 mg, 0.050 mmol) were added under an argon atmosphere, and the suspension was stirred at room temperature for 5 min to become a clear solution. Then 4-(2-methylallyloxy)-but-2-ynoic acid methyl ester (1a) (84.0 mg, 0.500 mmol) was added under an argon atmosphere.…”

Section: 5ј-diylbis(diphenylphosphine) [(S)-segphos] Were Provided mentioning

confidence: 99%

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Palladium-catalyzed carbocyclization of 1,6-enynes leading to six-membered rings or oxidized five-membered trifluoroacetates

Mikami

Hatano

2004

Proc. Natl. Acad. Sci. U.S.A.

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We describe palladium-catalyzed carbocyclization of 1,6-enynes leading to six-membered rings by water-originated hydride addition. Mechanistic features of this anomalous carbocyclization and isolation of a chiral five-membered C-Pd intermediate as an oxidized form of trifluoroacetate are also reported.T ransition metal-catalyzed carbocyclizations of 1,6-enynes A (1-4), such as cycloisomerization (5-11), metathesis (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), skeletal reorganization (23-26), and ene reactions (27)(28)(29), are useful synthetic methods leading to five-membered rings (Scheme 1). By contrast, we challenged six-membered cyclization of 1,6-enynes of type B by alkyne-metal-or carbonyl (Y ϭ CAO)-Lewis acid complexation by 6-(2, 4) ene-type cyclization (30) (after [1,5]-hydrogen shift numbering) (Oppolzer's type II) (31) (Scheme 2). A six-membered ring was obtained, however, not as the expected (Z)-olefin C. Herein, we report that dicationic palladium-catalyzed carbocyclization of 1,6-enynes (32, 33), unlike ruthenium-, rhodium-, and platinum-catalyzed metathesis, leads to the (E)-six-membered rings (D), wherein water-derived hydride is involved to fix the (E)-olefin geometry. We also present the mechanistic features of this anomalous carbocyclization and isolation of a chiral five-membered C-Pd intermediate (E) as an oxidized trif luoroacetate. MethodsGeneral. 1 H, 13 C, and 31 P NMR spectra were measured on Varian Gemini 300 (300 MHz) and Varian Gemini 400 (400 MHz) spectrometers. IR spectra were measured on a FT͞IR-5000 spectrometer (Jasco, Tokyo). Optical rotations were measured on a Jasco DIP-370. Liquid chromatographic analyses (HPLC) were conducted on a Jasco PU-980, LG-980 -02, DG-980 -50, AS-950, and CO-966 instrument equipped with model UV-975 spectrometers as an ultraviolet light. Peak areas were calculated by JASCO-BORWIN (WINDOWS NT) as an automatic integrator. Capillary GC analyses were conducted on a Shimadzu GC-14B instrument by using N 2 (75 kPa) as a carrier gas. Peak areas were calculated by a Shimadzu C-R6A as an automatic integrator; chiral columns were CPCyclodextrin-␤-2,3,6-M-19 (i.d. 0.25 mm ϫ 25 m; Chrompack, GL Sciences, Tokyo) and CP-Chirasil-Dex CB (i.d. 0.32 mm ϫ 25 m; Chrompack, GL Sciences). The split ratio was 100:1. Analytical TLC was performed on glass plates (Merck Kieselgal 60 F 254 ; layer thickness, 0.25 and 0.2 mm). Visualization was accomplished by UV light (254 nm), anisaldehyde, KMnO 4 , and phosphomolybdic acid. Column chromatography was performed on Kanto Silica Gel 60N (spherical, neutral; Kanto Kagaku, Tokyo). All experiments were carried out under an argon atmosphere unless otherwise noted. 5,5Ј-diylbis(diphenylphosphine) [(S)-SEGPHOS] were provided by Takasago International (Tokyo).Typical Procedure for Pd-Catalyzed Ene-Type Cyclization. To a Pyrex test tube well degassed DMSO (2.0 ml) was injected, and argon was charged. [(MeCN) 4 Pd](BF 4 ) 2 (11.1 mg, 0.025 mmol) and (R)-BINAP (17.1 mg, 0.050 mmol) were added under an argon atmosphere, and the suspensi...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: 5ј-diylbis(diphenylphosphine) [(S)-segphos] Were Provided mentioning

confidence: 99%

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Palladium-catalyzed carbocyclization of 1,6-enynes leading to six-membered rings or oxidized five-membered trifluoroacetates

Mikami

Hatano

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…[3][4][5][6] Selective carbocyclization by activation of unsaturated C-C multiple bonds in acyclic precursors under transition metal catalyses plays a relevant role in this context mainly thanks to its unique possibility to overcome limitations connected to other conventional methods. 4,[7][8][9][10][11][12][13][14][15][16][17] In this field, gold-catalyzed cycloisomerization reactions of poly-unsaturated substrates received the attention of many research groups in the last few years. [18][19][20] Recently, a straightforward access to polyconjugated Gold catalyst Scheme 1.…”

Section: Introductionmentioning

confidence: 99%