Organophosphorus-catalyzed diaza-Wittig reaction: application to the synthesis of pyridazines

Abed, Hassen Bel; Mammoliti, Oscar; Bande, Omprakash; Lommen, Guy Van; Herdewijn, Piet

doi:10.1039/c4ob01201a

Cited by 28 publications

(7 citation statements)

References 44 publications

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“…The common thread uniting these two sequential reduction events is the action of the small-ring phosphacycle 1 ·[O] to catalyze O-atom transfer by redox cycling in the P(III)/P(V) couple. Since O’Brien’s initial report of an organophosphorus-catalyzed Wittig reaction, , P(III)/P(V) redox catalysis has emerged as an productive area of organophosphorus catalysis, − with work from Woerpel, Rutjes and van Delft, Werner, Mecinović, Kwon, and Voituriez, among others. − In the context of the current C–N coupling method, the observation that the resting state of the catalyst resides at the P(III) oxidation state (i.e., phosphetane 1 ) confirms the swift deoxygenation kinetics of small-ring phosphine oxides noted by Marsi and Keglevich and makes clear that P(V)O→P(III) turnover is not a significant impediment to method development in the P(III)/P(V) couple with these catalytic structures.…”

Section: Discussionmentioning

confidence: 99%

An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

Nykaza

Cooper

et al. 2020

J. Am. Chem. Soc.

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Experimental, spectroscopic, and computational studies are reported that provide an evidence-based mechanistic description of an intermolecular reductive C−N coupling of nitroarenes and arylboronic acids catalyzed by a redox-active maingroup catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide, i.e., 1• [O]). The central observations include the following: (1) catalytic reduction of 1•[O] to P III phosphetane 1 is kinetically fast under conditions of catalysis; (2) phosphetane 1 represents the catalytic resting state as observed by 31 P NMR spectroscopy; (3) there are no long-lived nitroarene partial-reduction intermediates observable by 15 N NMR spectroscopy; (4) the reaction is sensitive to solvent dielectric, performing best in moderately polar solvents (viz. cyclopentylmethyl ether); and (5) the reaction is largely insensitive with respect to common hydrosilane reductants. On the basis of the foregoing studies, new modified catalytic conditions are described that expand the reaction scope and provide for mild temperatures (T ≥ 60 °C), low catalyst loadings (≥2 mol%), and innocuous terminal reductants (polymethylhydrosiloxane). DFT calculations define a two-stage deoxygenation sequence for the reductive C−N coupling. The initial deoxygenation involves a ratedetermining step that consists of a (3+1) cheletropic addition between the nitroarene substrate and phosphetane 1; energy decomposition techniques highlight the biphilic character of the phosphetane in this step. Although kinetically invisible, the second deoxygenation stage is implicated as the critical C−N product-forming event, in which a postulated oxazaphosphirane intermediate is diverted from arylnitrene dissociation toward heterolytic ring opening with the arylboronic acid; the resulting dipolar intermediate evolves by antiperiplanar 1,2-migration of the organoboron residue to nitrogen, resulting in displacement of 1•[O] and formation of the target C−N coupling product upon in situ hydrolysis. The method thus described constitutes a mechanistically well-defined and operationally robust main-group complement to the current workhorse transition-metal-based methods for catalytic intermolecular C−N coupling.

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Section: Discussionmentioning

confidence: 99%

An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

Nykaza

Cooper

et al. 2020

J. Am. Chem. Soc.

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“…Other applications of iminophosphorane intermediates in the context of P III /P V O cycling include catalytic aza-Wittig − and diaza-Wittig reactions (Figure A) . In 2018, Kwon demonstrated the first catalytic asymmetric Staudinger-aza-Wittig reaction , with high levels of stereoinduction via desymmetrization of diketones using HypPhos catalyst P12 with the assistance of a Brønsted acid additive (Figure B) …”

Section: State-of-the-art Developments In Organopnictogen Redox Catal...mentioning

confidence: 99%

Main Group Redox Catalysis of Organopnictogens: Vertical Periodic Trends and Emerging Opportunities in Group 15

2021

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A growing number of organopnictogen redox catalytic methods have emergedespecially within the past 10 yearsthat leverage the plentiful reversible two-electron redox chemistry within Group 15. The goal of this Perspective is to provide readers the context to understand the dramatic developments in organopnictogen catalysis over the past decade with an eye toward future development. An exposition of the fundamental differences in the atomic structure and bonding of the pnictogens, and thus the molecular electronic structure of organopnictogen compounds, is presented to establish the backdrop against which organopnictogen redox reactivityand ultimately catalysisis framed. A deep appreciation of these underlying periodic principles informs an understanding of the differing modes of organopnictogen redox catalysis and evokes the key challenges to the field moving forward. We close by addressing forward-looking directions likely to animate this area in the years to come. What new catalytic manifolds can be developed through creative catalyst and reaction design that take advantage of the intrinsic redox reactivity of the pnictogens to drive new discoveries in catalysis?

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“…In 2014, the Herdewijn group reported the first example of an organophosphorus-catalyzed diaza-Wittig reaction and its application to construct pyridazine and phthalazine derivatives (Scheme 859). 966 Various substrates containing a diazo functionality were examined as starting materials. Most of the pyridazines bearing electron-withdrawing groups were obtained as precipitates in good to excellent yields.…”

Section: Miscellaneous Topicsmentioning

confidence: 99%

Phosphine Organocatalysis

et al. 2018

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The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon–carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita–Baylis–Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material—nucleophiles, dinucleophiles, electrophiles, and electrophile–nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon–carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon–carbon multiple bond–containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide–generating reactions.

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Organophosphorus-catalyzed diaza-Wittig reaction: application to the synthesis of pyridazines

Cited by 28 publications

References 44 publications

An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

Main Group Redox Catalysis of Organopnictogens: Vertical Periodic Trends and Emerging Opportunities in Group 15

Phosphine Organocatalysis

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Organophosphorus-catalyzed diaza-Wittig reaction: application to the synthesis of pyridazines

Cited by 28 publications

References 44 publications

An Improved PIII/PV═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

An Improved PIII/PV═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

Main Group Redox Catalysis of Organopnictogens: Vertical Periodic Trends and Emerging Opportunities in Group 15

Phosphine Organocatalysis

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Product

Resources

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An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps

An Improved P^III/P^V═O-Catalyzed Reductive C–N Coupling of Nitroaromatics and Boronic Acids by Mechanistic Differentiation of Rate- and Product-Determining Steps