scispace - formally typeset
Search or ask a question

Showing papers on "Dichlorophenylphosphine published in 1993"


Journal ArticleDOI
TL;DR: In this paper, the synthesis and reactions of new phosphine-boranes have been studied and new methods for the synthesis of bidentate phosphine ligands with homochiral phosphine centers were developed.
Abstract: Synthesis and reactions of new phosphine-boranes have been studied. Diastereomerically pure menthyloxyphenylphosphine-boranes were prepared from dichlorophenylphosphine. These secondary phosphine-boranes underwent stereospecific alkylation and arylation reactions. It is noted that the stereochemistry of palladium-catalyzed cross-coupling reactions was largely affected by the solvent and the base used. Thus, the reaction in acetonitrile proceeded with net retention of configuration. In sharp contrast, the reaction in THF in the presence of K2CO3 occurred with inversion of configuration with high degree of stereospecificity. The phosphorus-oxygen bond of the resulting phosphine-boranes was reductively cleaved at -78 "C by lithium naphthalenide or lithium in liquid ammonia in almost quantitative yields with an excellent degree of stereospecificity. On the other hand, the reactions at elevated temperatures provided the products with almost complete racemization. This racemization was proved to occur via pyramidal inversion of the anionic tricoordinate phosphorus species. Based on these results, we developed new methods for the synthesis of bidentate phosphine ligands with homochiral phosphine centers. Optically pure bisphosphinoethanes and bisphosphinobutanes possessing phenyl, t-butyl, cyclohexyl, emethomhenyl, methyl, or 2methoxyethyl group were prepared via phosphine-boranes. Functionalizations of the boranato group of phosphine-boranes have been investigated. Trimethylphosphine-borane reacted with methanesulfonic acid with evolution of hydrogen. The resulting trimethylphosphine-methylsulfonyloxyborane was subjected to nucleophilic substitution reaction on the boron atom with arenthiols or secondary phosphine-boranes. A new phosphine-borane having a P-B-P-B-P-B-P-B bond linkage was synthesized. Novel boron anion species were generated by the reaction of phosphine-monoiodoboranes with lithium 4,4'-dit -butylbiphenylide.

80 citations


Journal ArticleDOI
Tsuneo Imamoto1
TL;DR: In this paper, a new method for the synthesis of phosphine-boranes including optically active ones has been established, based on the stereochemical studies on the substitution reactions at chiral phosphorus.
Abstract: New methods for the synthesis of phosphine-boranes including optically active ones have been established. Diphenylphosphine-borane and methyldiphenylphosphine-borane reacted with various electrophiles to give phosphine-borane derivatives having a functional group. Diastereomerically pure secondary phorphine-boranes, (Sp) -and (Rp) -menthyloxyphenylphosphine-boranes, were prepared from dichlorophenylphosphine. These secondary phosphine-boranes underwent stereospecific alkylation and arylation reactions. The phosphorus-oxygen bond of the resulting phosphine-boranes was reductively cleaved by lithium naphthalenide in an almost quantitative yield with virtually net retention of configuration. A new and efficient route to bidentate phosphine ligands with homochiral phosphine center has been established on the basis of these stereochemical studies on the substitution reactions at chiral phosphorus. Functionalizations of the boranato group of phosphine-boranes have been investigated. Trialkylphosphine-boranes reacted with methanesulfonic acid or trifluoromethanesulfonic acid with evolution of hydrogen The resulting sulfonates were subjected to nucleophilic substitution reactions with various nucleophiles including carbon nucleophiles. A new phosphine-borane having a P-B-P-B-P-B-P-B bond linkage was synthesized.

11 citations


Journal ArticleDOI
TL;DR: In this article, the 4-bromo derivative of 2H was obtained as a 75% Z, 25% E diastereomer mixture from which pure (Z)-2Br can be isolated.
Abstract: Reaction of 2,2,6,6-tetramethyl-4-heptyn-3-0l with dichlorophenylphosphine leads to 2,2,6,6-tetramethyl-3,4-heptadien-3-1 phenyl phosphinic acid (11, which undergoes Ag+-catalyzed cyclization to 3,5-di-t-butyl-2-phenyl-1,2-oxaphosphol-3-ene 2-oxide (2H, 75-55% z, 25–45% E). Electrophilic bromination of 1 affords 2Br, the 4-bromo derivative of 2H, as a 75% Z, 25% E diastereomer mixture from which pure (Z)-2Br can be isolated.

2 citations


Journal ArticleDOI
Tsuneo Imamoto1
TL;DR: In this paper, a new method for the synthesis of phosphine-boranes including optically active ones has been established, based on the stereochemical studies on the substitution reactions at chiral phosphorus.
Abstract: New methods for the synthesis of phosphine-boranes including optically active ones have been established. Diphenylphosphine-borane and methyldiphenylphosphine-borane reacted with various electrophiles to give phosphine-borane derivatives having a functional group. Diastereomerically pure secondary phorphine-boranes, (Sp) -and (Rp) -menthyloxyphenylphosphine-boranes, were prepared from dichlorophenylphosphine. These secondary phosphine-boranes underwent stereospecific alkylation and arylation reactions. The phosphorus-oxygen bond of the resulting phosphine-boranes was reductively cleaved by lithium naphthalenide in an almost quantitative yield with virtually net retention of configuration. A new and efficient route to bidentate phosphine ligands with homochiral phosphine center has been established on the basis of these stereochemical studies on the substitution reactions at chiral phosphorus. Functionalizations of the boranato group of phosphine-boranes have been investigated. Trialkylphosphine-boranes reacted with methanesulfonic acid or trifluoromethanesulfonic acid with evolution of hydrogen The resulting sulfonates were subjected to nucleophilic substitution reactions with various nucleophiles including carbon nucleophiles. A new phosphine-borane having a P-B-P-B-P-B-P-B bond linkage was synthesized.

Journal ArticleDOI
Tsuneo Imamoto1
TL;DR: In this paper, the synthesis and reactions of new phosphine-boranes have been studied and new methods for the synthesis of bidentate phosphine ligands with homochiral phosphine centers were developed.
Abstract: Synthesis and reactions of new phosphine-boranes have been studied. Diastereomerically pure menthyloxyphenylphosphine-boranes were prepared from dichlorophenylphosphine. These secondary phosphine-boranes underwent stereospecific alkylation and arylation reactions. It is noted that the stereochemistry of palladium-catalyzed cross-coupling reactions was largely affected by the solvent and the base used. Thus, the reaction in acetonitrile proceeded with net retention of configuration. In sharp contrast, the reaction in THF in the presence of K2CO3 occurred with inversion of configuration with high degree of stereospecificity. The phosphorus-oxygen bond of the resulting phosphine-boranes was reductively cleaved at -78 "C by lithium naphthalenide or lithium in liquid ammonia in almost quantitative yields with an excellent degree of stereospecificity. On the other hand, the reactions at elevated temperatures provided the products with almost complete racemization. This racemization was proved to occur via pyramidal inversion of the anionic tricoordinate phosphorus species. Based on these results, we developed new methods for the synthesis of bidentate phosphine ligands with homochiral phosphine centers. Optically pure bisphosphinoethanes and bisphosphinobutanes possessing phenyl, t-butyl, cyclohexyl, emethomhenyl, methyl, or 2methoxyethyl group were prepared via phosphine-boranes. Functionalizations of the boranato group of phosphine-boranes have been investigated. Trimethylphosphine-borane reacted with methanesulfonic acid with evolution of hydrogen. The resulting trimethylphosphine-methylsulfonyloxyborane was subjected to nucleophilic substitution reaction on the boron atom with arenthiols or secondary phosphine-boranes. A new phosphine-borane having a P-B-P-B-P-B-P-B bond linkage was synthesized. Novel boron anion species were generated by the reaction of phosphine-monoiodoboranes with lithium 4,4'-dit -butylbiphenylide.