- Palladium-catalyzed reactions of hypophosphorous compounds with allenes, dienes, and allylic electrophiles: Methodology for the synthesis of allylic H-phosphinates
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(Chemical Equation Presented) Hypophosphorous compounds (MOP(O)H 2, M = H, R3NH) effectively participate in metal-catalyzed C-P bond-forming reactions with allenes, dienes, and activated allylic electrophiles under mild conditions. The catalytic system Pd2dba 3/xantphos is crucial to avoid or minimize the competitive reductive transfer-hydrogenation pathway available to hypophosphorous acid derivatives. Further investigation into the allylation mechanism provided access to the analogy allylic acetate - allylic phosphinate, which then led to the development of a Pd-catalyzed rearrangement of preformed allylic phosphinates esters and, ultimately, to a catalytic dehydrative allylation of hypophosphorous acid with allylic alcohols. The reactions disclosed herein constitute efficient synthetic approaches, not only to prepare allylic H-phosphinic acids but also their esters via one-pot tandem processes. In addition, the potential of H-phosphinates as useful synthons for the preparation of other organophosphorous compounds is demonstrated.
- Bravo-Altamirano, Karla,Abrunhosa-Thomas, Isabelle,Montchamp, Jean-Luc
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p. 2292 - 2301
(2008/09/19)
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- Direct monoalkylation of alkyl phosphinates to access H-phosphinic acid esters
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Simple alkyl phosphinates prepared by the silicate esterification method can be alkylated under Barbier-like conditions with butyl lithium at -78 °C followed by warming to room temperature. The method is limited to the more reactive electrophile such as allylic bromides and alkyl iodides. With these electrophiles good yields of H-phosphinic acid esters are generally obtained in a straightforward manner. Georg Thieme Verlag Stuttgart.
- Abrunhosa-Thomas, Isabelle,Ribiere, Patrice,Adcock, Alicia C.,Montchamp, Jean-Luc
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p. 325 - 331
(2007/10/03)
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- Palladium-catalyzed dehydrative allylation of hypophosphorous acid with allylic alcohols
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A novel palladium-catalyzed allylation of H3PO2 with allylic alcohols is described. The phosphorus-carbon bond-forming reaction produces allylic-H-phosphinic acids and water, in the absence of additives. Primary H-phosphinic acids are obtained in excellent yields, whereas secondary H-phosphinic acids react sluggishly. A reusable polymer-supported catalyst is also described. The reaction provides an environmentally sound approach to H-phosphinic acids.
- Bravo-Altamirano, Karla,Montchamp, Jean-Luc
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p. 4169 - 4171
(2007/10/03)
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- Palladium-catalyzed phosphorus-carbon bond formation: Cross-coupling reactions of alkyl phosphinates with aryl, heteroaryl, alkenyl, benzylic, and allylic halides and triflates
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The direct formation of H-arylphosphinates and related compounds can be accomplished using palladium catalysis. This full paper examines the scope and some mechanistic aspects of this phosphorus-carbon bond forming reaction. The reactions of alkenyl and allylic halides are also described for the first time. This novel cross-coupling provides a convenient access to a variety of substituted H-phosphinates.
- Bravo-Altamirano, Karla,Huang, Zhihong,Montchamp, Jean-Luc
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p. 6315 - 6329
(2007/10/03)
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- NiCl2-catalyzed hydrophosphinylation
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A new nickel-based catalytic system has been developed for phosphorus-carbon bond formation. The addition of alkyl phosphinates to alkynes is catalyzed by nickel chloride in the absence of added ligand. The reaction generally proceeds in high yields, even with internal alkynes, which were poor substrates in our previously reported palladium-catalyzed hydrophosphinylation of alkyl phosphinates. The method is useful for the preparation of H-phosphinate esters and their derivatives. The one-pot synthesis of various important organophosphorus compounds is also demonstrated. The reaction can be conducted with microwave heating.
- Ribiere, Patrice,Bravo-Altamirano, Karla,Antczak, Monika I.,Hawkins, Jennifer D.,Montchamp, Jean-Luc
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p. 4064 - 4072
(2007/10/03)
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