The asymmetric synthesis of α-substituted α-methyl and α-phenyl phosphonic acids: Design, carbanion geometry, reactivity and preparative aspects of chiral alkyl bicyclic phosphonamides

Bennani, Youssef L.; Hanessian, Stephen

doi:10.1016/0040-4020(96)00829-0

Cited by 68 publications

(34 citation statements)

References 73 publications

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“…The stereochemistry of the major compounds 5 and 10 was identified, after chromatographic purification, by hydrolysis to the known phosphonic acids. 15 Under the described experimental conditions, but using n-BuLi (2 equiv) as base, 4 led to a mixture of 10 and 11 (72:28, entry 5 in Table 1), whereas 1 yielded the alkylation product at the benzylic position of the nitrogen 7 in 64%, as a single diastereomer (entry 2 in Table 1). …”

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confidence: 98%

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Pedrosa¹,

Maestro²,

Pérez‐Encabo³

et al. 2004

Synlett

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The regioselectivity in the alkylation of chiral perhydro 1,3,2-benzoxazaphosphorinane-2-oxides is dependent on the base used for deprotonation. The ethyl oxazaphosphorinanes are benzylated at the nitrogen substituent after deprotonation with n-BuLi, but a to the phosphorous atom by deprotonation with LDA. On the contrary, the benzyl oxazaphosphorinane is alkylated a to the phosphorous atom after deprotonation with both, n-BuLi or LDA.

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confidence: 98%

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Pedrosa¹,

Maestro²,

Pérez‐Encabo³

et al. 2004

Synlett

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“…The stereochemistry at the created stereocenter was assigned for the major diastereoisomer 8a by hydrolysis into the known (R)-2-methyl-3phenylethyl phosphonic acid. 19 Interestingly, the axially substituted phosphorinane 2 did not react under these experimental conditions with the described electrophiles.…”

Section: Scheme 1 Synthesis Of Oxazaphosphorinanes 1-6mentioning

confidence: 88%

Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Amino Menthol

López¹,

Maestro²,

Pedrosa³

2006

Synthesis

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Chiral oxazaphosphorinanes, derived from (-)-8-amino menthol are alkylated with good to excellent diastereoselectivities. The regioselectivity in the alkylation is dependent on the base used for deprotonation. The ethyl oxazaphosphorinanes are alkylated at the nitrogen substituent after deprotonation with n-butyllithium, but in a-position to the phosphorous atom by deprotonation with LDA. On the contrary, the oxazaphosphorinanes with an alkyl substituent at the nitrogen atom or benzyl oxazaphosphorinane are alkylated in a-position to the phosphorous atom after deprotonation with either n-butyllithium or LDA.Phosphorous derivatives are an attractive class of compounds as a consequence of their biological 1 and chemical interest. In this respect, they have been used as starting materials in the synthesis of different classes of organic compounds 2 or as catalysts in enantioselective transformations. 3 In addition, phosphorous stabilized carbanions are one of the most powerful class of reagents for the selective construction of single 4 and double 5 carbon-carbon bonds.Specially interesting are chiral carbanions stabilized by a phosphorous atom because they allow for the diastereoselective formation of carbon-carbon bonds, and compounds with stereogenic phosphorous atoms and derivatives modified by chiral auxiliaries have been successfully used in this way. 6 Phosphonamides 7 and oxaphosphonamides 8 derived from chiral diamines or amino alcohols participate in diastereoselective transformations with excellent diastereomeric excess.The stereoselection observed in the reactions of phosphonamides and oxaphosphonamides has been rationalized on the basis of the steric and conformational preferences of both the neutral compounds 9 and the lithium derivatives, 10 although it is also dependent on the structure of the electrophile, 11 the stereochemistry of the phosphorous atom, 12 the nature of the substituents at the nitrogen atom, 8b and the size 13 and the configurational and conformational characteristics of the heterocyle. 14 Recently we have demonstrated that the regio-and stereochemistry of the alkylation of oxazaphosphorinanes is also dependent on the nature of the substituents at the phosphorous and nitrogen atoms and on the base used in the initial deprotonation, 15 and now we report in full our results on this type of diastereoselective alkylation on oxazaphosphorinanes with different substituents at the nitrogen and phosphorous atoms.The starting perhydro 1,3,2-oxazabenzophosphorinane-2-oxides (1-6) were prepared as summarized in Scheme 1. Compounds 1 (31%) and 2 (61%) were obtained by direct cyclization 16 of (-)-8-benzylamino menthol with ethyl phosphonic dichloride and triethylamine in dichloromethane, whereas diastereoisomers 3 and 4 (ca. 1:2 ratio) was prepared in the same way but starting from (-)-8-ethylamino menthol. Alternatively, compounds 6 (as a single diastereoisomer) and 1 (accompanied in ca. 3% by 2) were prepared by Arbuzov reaction, in refluxing toluene, between benzyl bromide or ethyl iodide a...

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“…DCDADQ was synthesized using the general strategy we have developed earlier . ( S , S ), ( R , R ) and racemic N , N′ ‐dimethylcyclohexane‐1,2‐diamine prepared from the respective cyclohexane‐1,2‐diamines, were reacted with 7‐pyrrolidino‐7,8,8‐tricyanoquinodimethane to yield DCDADQ (Figure S1, Note S1); the new compounds were recrystallized from acetonitrile. Crystals were grown from acetonitrile solution by cooling or evaporation; the ( S , S ) enantiomer yielded two crystalline forms, needle‐like DCDADQ‐ SS1 and rhombus‐shaped DCDADQ‐ SS2 , whereas the racemate gave one, DCDADQ‐ Rac .…”

Section: Basic Crystallographic and Molecular Structural Data (θ And mentioning

confidence: 99%

Establishing the Critical Role of Oriented Aggregation in Molecular Solid State Fluorescence Enhancement

Srujana

Radhakrishnan

2018

Chemistry A European J

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The general occurrence of fluorescence emission quenching in molecular aggregates is circumvented in select classes of molecules. This has largely been attributed to the rigidification of the molecule and its environment, which hinders non-radiative excited state energy loss through structural relaxation; since such an effect should in principle apply to most aggregates and crystals, there must clearly be other critical factors that make the select molecules exceptional. Discovery of three crystalline structures of a new push-pull molecule in its enantiomorphic and racemic forms, exhibiting not only very high, but distinctly different solid state fluorescence enhancements, has now allowed a systematic investigation of the role of intramolecular and intermolecular excited state energy loss pathways. Crystallographic, spectroscopic and computational investigations provide a detailed appraisal of the assembly patterns in the crystals, and rigorous establishment of an inverse correlation between intermolecular energy transfer and solid state fluorescence. The study provides a clear visualization of the critical role of oriented molecular aggregation in solid state fluorescence efficiency enhancement.

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The asymmetric synthesis of α-substituted α-methyl and α-phenyl phosphonic acids: Design, carbanion geometry, reactivity and preparative aspects of chiral alkyl bicyclic phosphonamides

Cited by 68 publications

References 73 publications

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Amino Menthol

Establishing the Critical Role of Oriented Aggregation in Molecular Solid State Fluorescence Enhancement

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The asymmetric synthesis of α-substituted α-methyl and α-phenyl phosphonic acids: Design, carbanion geometry, reactivity and preparative aspects of chiral alkyl bicyclic phosphonamides

Cited by 68 publications

References 73 publications

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Base-Dependent Regio- and Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Benzylamino Menthol

Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophos­phorinane-2-oxides Derived from (-)-8-Amino Menthol

Establishing the Critical Role of Oriented Aggregation in Molecular Solid State Fluorescence Enhancement

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Diastereoselective Alkylation of Chiral Perhydro 1,3,2-Oxazabenzophosphorinane-2-oxides Derived from (-)-8-Amino Menthol