Enantioselective Synthesis of P-Stereogenic Benzophospholanes via Palladium-Catalyzed Intramolecular Cyclization

Brunker, Tim J.; Anderson, B. J.; Blank, Natalia F.; Glueck, David S.; Rheingold, Arnold L.

doi:10.1021/ol0700512

Cited by 82 publications

(28 citation statements)

References 27 publications

(46 reference statements)

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“…[8] In addition, secondary phosphines have been used as nucleophiles in asymmetric conjugate addition, [9] alkylation, [10] and arylation reactions. [11] However, in this process, the strong coordination ability of the secondary phosphines may lead to deactivation of the metal catalyst, thereby reducing the enantioselectivity. Therefore, the development of alternative methods for the synthesis of P-chiral compounds is still highly necessary.Compared with secondary phosphines, secondary phosphine oxides (SPOs) are more stable in air and have low toxicity to metal catalysts.…”

mentioning

confidence: 99%

Cobalt‐Catalysed Asymmetric Addition and Alkylation of Secondary Phosphine Oxides for the Synthesis of P‐Stereogenic Compounds

Weng

Cheng

et al. 2021

Angewandte Chemie

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The catalytic asymmetric synthesis of P-chiral phosphorus compounds is an important way to construct Pchiral ligands. Herein, we report a new strategy that adopts the pyridinyl moiety as the coordinating group in the cobaltcatalysed asymmetric nucleophilic addition/alkylation of secondary phosphine oxides. A series of tertiary phosphine oxides were generated with up to 99 % yield and 99.5 % ee, and with broad functional-group tolerance. Mechanistic studies reveal that (R)-secondary phosphine oxides preferentially interact with the cobalt catalysts to produce P-stereogenic compounds.Chiral phosphorus compounds play important roles as ligands [1] or organic catalysts [2] in asymmetric catalysis. Compared to the synthesis of axial-, planar-, and carboncentered chiral phosphorus compounds, the synthesis of Pstereogenic phosphines has been less investigated. The main recent strategies for the preparation of P-chiral compounds involve the use of chiral auxiliary materials or the resolution of racemates. [3] These classical methods require stoichiometric chiral agents or generate an equivalent amount of compound with an opposite configuration. [4] Recently, several asymmetric catalytic methods were developed based on the desymmetrization of phosphine oxides via CÀH bond activation, [5] asymmetric addition, [6] ring-closing metatheses, [7] and [2+2+2] cycloaddition processes. [8] In addition, secondary phosphines have been used as nucleophiles in asymmetric conjugate addition, [9] alkylation, [10] and arylation reactions. [11] However, in this process, the strong coordination ability of the secondary phosphines may lead to deactivation of the metal catalyst, thereby reducing the enantioselectivity. Therefore, the development of alternative methods for the synthesis of P-chiral compounds is still highly necessary.Compared with secondary phosphines, secondary phosphine oxides (SPOs) are more stable in air and have low toxicity to metal catalysts. Nonetheless, only a few synthetic examples have been reported for the preparation of optically active tertiary phosphine oxides (TPOs) from SPOs. In 2016, Gaunt and co-workers reported a new strategy in which Cu combined with chiral pyridine-2,6-bis(oxazolines) ligand (pybox) was applied for the enantioselective arylation of SPOs with diaryliodonium salt, affording P-chiral tertiary phosphorus compounds with up to 98 % ee (Scheme 1 a). [12] The Cai group reported a Pd-catalysed arylation of SPOs with aryl iodides with moderate to high ee (Scheme 1 b). [13] Recently, Zhang and co-workers also reported Pd-catalysed asymmetric arylation and alkenylation reactions of SPOs (Scheme 1 c), in which products were obtained in up to 99 % ee. [14] In addition to the above examples, the Qing-Wei Zhang group developed a Ni-catalysed kinetic resolution of SPOs via an allylic substitution process, providing a series of Pstereogenic compounds with high enantioselectivity (Scheme 1 d). [15] However, the SPOs in the abovementioned examples usually contain one aryl and one alkyl group. Substrates b...

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confidence: 99%

Cobalt‐Catalysed Asymmetric Addition and Alkylation of Secondary Phosphine Oxides for the Synthesis of P‐Stereogenic Compounds

Weng

Cheng

et al. 2021

Angewandte Chemie

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“…hexylphosphine 17b reacted much more quickly, it gave the racemic product 18b as a result of catalyst decomposition. 24 A similar problem arising with the use of small, nucleophilic substrates was observed in Natalia Blank's studies with dialkylphosphine 19 (Scheme 11). The Pd[(R,R)-i-Pr-Duphos]-mediated cross-coupling of 19 with phenyl iodide gave 20 in 91% diastereomeric excess (de), but the analogous (R,R)-Me-Duphos catalyst decomposed to Pd(Me-Duphos) 2 during the reaction.…”

Section: Secondary Phosphinesmentioning

confidence: 63%

Metal-Catalyzed Asymmetric Synthesis of P-Stereogenic Phosphines

Glueck¹

2007

Synlett

151

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This account summarizes our attempts to develop metalcatalyzed asymmetric syntheses of P-stereogenic phosphines. While such phosphines undergo pyramidal inversion slowly at room temperature, inversion is rapid in metal-phosphido complexes (M-PR 2 ). These observations were the basis for catalytic, dynamic kinetic resolution processes in which racemic secondary phosphines [PR(R¢)H] were converted into enantioenriched tertiary phosphines [PR(R¢)(R¢¢)] by platinum-catalyzed asymmetric hydrophosphination of acrylonitrile or related Michael acceptors, by palladium-catalyzed asymmetric phosphination of aryl iodides using secondary phosphines or phosphine-boranes, and by platinumcatalyzed asymmetric alkylation of secondary phosphines. The key intermediates were diastereomeric phosphido complexes with chiral ancillary ligands (L n *-M-PRR¢). Their relative rates of P-inversion and phosphorus-carbon bond formation controlled the enantioselectivity of product formation, whether the phosphoruscarbon bonds were formed by reductive elimination (for Pd), or by the reaction of a platinum-phosphido complex with an electrophile (an alkene in hydrophosphination, or a benzyl bromide in alkylation). The results of mechanistic studies and their use in the design of improved catalytic reactions are described.

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“…Similar cross-couplings have been used in enantioselective ring-closing to form benzophospholanes (Scheme 47) [79]. …”

Section: Asymmetric Phosphinationmentioning

confidence: 99%

Recent Advances in Metal-Catalyzed C–P Bond Formation

Glueck

2010

C-X Bond Formation

Self Cite

158

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This chapter describes recent advances in metal-catalyzed C-P bond formation, which may be classified into two types of reactions. In hydrophosphination and related processes, P-H groups add across unsaturated C-X (X ¼ C, N, O) bonds. Phosphination of electrophiles typically results in substitution at sp 2 or sp 3 carbon; the P-H group is removed, often by a base. The scope of both nucleophilic and electrophilic partners in these processes is surveyed, and the proposed mechanisms and intermediates in the metal-catalyzed reactions are described.

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Enantioselective Synthesis of P-Stereogenic Benzophospholanes via Palladium-Catalyzed Intramolecular Cyclization

Cited by 82 publications

References 27 publications

Cobalt‐Catalysed Asymmetric Addition and Alkylation of Secondary Phosphine Oxides for the Synthesis of P‐Stereogenic Compounds

Cobalt‐Catalysed Asymmetric Addition and Alkylation of Secondary Phosphine Oxides for the Synthesis of P‐Stereogenic Compounds

Metal-Catalyzed Asymmetric Synthesis of P-Stereogenic Phosphines

Recent Advances in Metal-Catalyzed C–P Bond Formation

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