Microwave‐Assisted Asymmetric Intermolecular Heck Reaction using Phosphine‐Thiazole Ligands

Kaukoranta, Päivi; Källström, Klas; Andersson, Pher G.

doi:10.1002/adsc.200700390

Cited by 44 publications

(20 citation statements)

References 33 publications

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“…[18] Scheme 6. [a] Conversions were determined using achiral GC with tri-n-decane as internal standard.…”

Section: Asymmetric Naphthylation Of 23-dihydrofuranmentioning

confidence: 99%

“…X-3: G. M. Sheldrick, SHELXL-97-2, University of Göttingen, 1997. Racemic samples of 2-phenyl-2,5-dihydrofuran (10), [9] 2-cylohex-1Ј-en-yl-2,5-dihydrofuran (3), [9] and 2-naphthalen-2Ј-yl-2,5-dihydrofuran (13) [18] were prepared and analysed according to literature reports. Conversions for asymmetric reactions were measured using burn ratios with tri-n-decane as internal standard.…”

Section: Generalmentioning

confidence: 99%

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The Synthesis of New HetPHOX Ligands and Their Application to the Intermolecular Asymmetric Heck Reaction

Fitzpatrick¹,

Müller‐Bunz²,

Guiry³

2009

Eur J Org Chem

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“…[18] Scheme 6. [a] Conversions were determined using achiral GC with tri-n-decane as internal standard.…”

Section: Asymmetric Naphthylation Of 23-dihydrofuranmentioning

confidence: 99%

Section: Generalmentioning

confidence: 99%

The Synthesis of New HetPHOX Ligands and Their Application to the Intermolecular Asymmetric Heck Reaction

Fitzpatrick¹,

Müller‐Bunz²,

Guiry³

2009

Eur J Org Chem

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“…In an attempt to identify improved chiral ligands for the asymmetric Mizoroki-Heck arylation of 2,3-dihydrofuran with aryl triflates, Andersson and co-workers investigated the identification of efficient phosphinethiazole ligands Yield [231]. In all cases investigated, the regioselectivity for arylation of the C2-position of the dihydrofuran was very high, whereas the enantioselectivity, reaction rate, and yield were dependent on the substitution patterns of the ligands (Scheme 15.122).…”

Section: The Heck Reaction 657mentioning

confidence: 99%

Microwave‐Heated Transition Metal‐Catalyzed Coupling Reactions

Russo

Odell

Olofsson

et al. 2012

Microwaves in Organic Synthesis

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“…Although ligands 7, 9 and 10 gave poorer %ee values than (R)-BINAP (8), and (R)-SYN-PHOS (16) and CTH-(R)-P-PHOS (13) gave similar %ee values to (R)-BINAP (8) ( Table 1, column 3), significant improvements in the %ee values were observed when (R)-C 1 -TUNEPHOS (14, 82% ee), (R)-C 3 -TUNEPHOS (15, 81% ee), (R)-SEGPHOS (12, 85% ee), and (R)-DIFLUOR-PHOS (11, 94% ee) were employed in the polyene cyclization. It is noteworthy, that the %ee with (R)-DIFLUORPHOS is the highest attained in this cyclization to date.…”

mentioning

confidence: 93%

Further Developments of an Enantioselective Palladium-Catalyzed Polyene Cyclization: Surprising Solvent and Ligand Effects

Lucciola¹,

Keay²

2011

Synlett

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The enantioselectivity of a Pd-catalyzed domino HeckMizoroki cyclization is dramatically enhanced by ligand and solvent choice. Electron-deficient ligands such as (R)-DIFLUORPHOS gave 5 in %ee values ranging from 94% ee to >99% ee. EtOH was found to be superior to other solvents traditionally used in HeckMizoroki reactions, generally showing increases in enantioselectivity when compared to toluene. It is also shown that microwave heating accelerates the reaction in either solvent and allows for a longer catalyst lifetime without eroding the %ee.The use of asymmetric domino reactions in synthetic sequences toward the preparation of natural products has become a powerful strategy as two or more rings and stereogenic centres can be formed in a single step often with high enantioselectivies. 1 Our group has previously employed an asymmetric palladium-catalyzed domino Heck-Mizoroki 2 cyclization as the key step (in 68% ee) in the synthesis of (+)-xestoquinone (3) (see 1 → 2, Scheme 1). 3 Since then we have been investigating a variety of methods to increase the %ee of the Pd-catalyzed polyene cyclization using 4 (Scheme 2) as a model system. These studies have included the use of: (1) substituents ortho to the triflate (96% ee); 4a (2) 3,3¢-disubstituted BIPHEP derivatives (72% ee); 4b (3) 7,7¢-and 3,3¢-disubstituted BINAP derivatives (74% ee); 4c,d and (4) 3,3¢-disubstituted xylBINAP derivatives (47% ee). 4e Interestingly, the use of any of the (S)-3,3¢-disubstituted BIPHEP or BINAP derivatives gave rise to 5 with the opposite sense of chirality when compared to the results using unsubstituted (S)-BIPHEP or (S)-BINAP. Although the best result to date was when a methyl group was ortho to the triflate in 4, (+)-xestoquinone (3) lacks this group so we continued our study on improving the %ee of this interesting Pd-catalyzed polyene cyclization and report herein that 5 can be formed in %ee values ranging from 94% to >99% using (R)-DIFLUORPHOS as the chiral ligand in EtOH using an oil bath or under microwave conditions.Recently, we carried out a new ligand study using the reaction conditions outlined in Scheme 2 with the ligands shown in Figure 1. Although ligands 7, 9 and 10 gave poorer %ee values than (R)-BINAP (8), and (R)-SYN-PHOS (16) and CTH-(R)-P-PHOS (13) gave similar %ee values to (R)-BINAP (8) ( Table 1, column 3), significant improvements in the %ee values were observed when (R)-C 1 -TUNEPHOS (14, 82% ee), (R)-C 3 -TUNEPHOS (15, 81% ee), (R)-SEGPHOS (12, 85% ee), and (R)-DIFLUOR-PHOS (11, 94% ee) were employed in the polyene cyclization. It is noteworthy, that the %ee with (R)-DIFLUORPHOS is the highest attained in this cyclization to date. Encouraged by these results, we wanted to examine other possibilities for further increasing the %ee and %yield of the polyene cyclization.Our attention turned toward microwave heating as a possible means to achieve higher enantioselectivities. Recently, microwave irradiation has been used in the studies of asymmetric (both enantioselective and diastereoselective) Heck react...

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Microwave‐Assisted Asymmetric Intermolecular Heck Reaction using Phosphine‐Thiazole Ligands

Cited by 44 publications

References 33 publications

The Synthesis of New HetPHOX Ligands and Their Application to the Intermolecular Asymmetric Heck Reaction

The Synthesis of New HetPHOX Ligands and Their Application to the Intermolecular Asymmetric Heck Reaction

Microwave‐Heated Transition Metal‐Catalyzed Coupling Reactions

Further Developments of an Enantioselective Palladium-Catalyzed Polyene Cyclization: Surprising Solvent and Ligand Effects

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