Asymmetric Induction by Chiral Phosphorus

Afarinkia, K.; Binch, Hayley; Forristal, Ian; Jones, Clare; Lowman, James; Pascale, Egizia De; Twist, Andrew

doi:10.1002/chin.200307245

Cited by 6 publications

(14 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, the similarity in the magnitude and the sense of selectivity in the additions of the phenyl anion suggests that the chiral induction in the additions to 2a or 2b and 5a or 5b, is determined primarily by the chirality at the phosphorus atom as previously proposed (Scheme 5). 2 This confirms our working model which rationalises the observed selectivities based on a combination of steric and internal chelation effects. …”

Section: Issn 1424-6376supporting

confidence: 84%

“…1 We have previously reported that these β-substituted phosphonamidates can be prepared diastereoselectively by the nucleophilic additions to asymmetric vinylphosphonamidates. 2,3 For instance additions of a variety of carbon nucleophiles to chiral racemic 3-diphenylmethyl-2-(prop-2-enyl)-1,3,2-oxazaphosphorinane-2-oxide 1, proceed with good selectivities (typically >80% de) and the relative configuration of the major diastereomers are (S P ,S C(β) /R P ,R C(β) ). Furthermore, the major isomer of these additions can be isolated after one crystallisation as a single diastereomer (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Asymmetric nucleophilic addition to vinylphosphonamidates (Part IV)

Afarinkia¹,

Pascale²,

Amara³

2002

Arkivoc

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Issn 1424-6376supporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Asymmetric nucleophilic addition to vinylphosphonamidates (Part IV)

Afarinkia¹,

Pascale²,

Amara³

2002

Arkivoc

Self Cite

View full text Add to dashboard Cite

show abstract

“…[1] These alkenylphosphonic (or -ate) groups can be constructed by several reactions [2] such as metal-catalyzed coupling reactions of alkenyl halides with HP(O)(OR) 2 [3] and P(OR) 3 , [4] rhodium-catalyzed addition of HP(O)(OR) 2 to acetylenes, [5] Heck reaction of vinylphosphonates, [6] Wittig-and aldol-type reactions of aldehydes with methylphosphonates, [7] isomerization of allylphosphonates, [8] etc. [9] These reactions allow the synthesis of the b-monoalkyl-substituted alkenylphosphonates, but are hardly suitable for more substituted alkenylphosphonates, which would be intermediates for advanced complex analogues.…”

Section: Introductionmentioning

confidence: 99%

Palladium‐ and Nickel‐Catalyzed Coupling Reactions of α‐Bromoalkenylphosphonates with Arylboronic Acids and Lithium Alkenylborates

Kobayashi

William

2004

Adv Synth Catal

View full text Add to dashboard Cite

show abstract

“…For our study, we chose compounds 1a, 1 1b 4 and 1c, 4 prepared as reported elsewhere ( Figure 1). Compound 1a, alkylation of which has been reported in the preceding paper, contains only one asymmetric phosphorus atom.…”

mentioning

confidence: 99%

Alkylation of Asymmetric Phosphonamidates (Part II)

Afarinkia¹,

Jones²

2003

Synlett

Self Cite

View full text Add to dashboard Cite

A l k y l a t i o n o f A s y m m e t r i c P h o s p h o n a m i d a t e sAbstract: The stereochemistry of the alkylation of phosphonamidates 1b is influenced mostly by the chirality of the asymmetric phosphorus atom and not by the chirality of the asymmetric carbon atom. In contrast, the stereochemistry of the alkylation of phosphonamidates 1c is influenced by a combination of the stereochemistry of the chiral phosphorus atom and the stereochemistry of the chiral carbon atom.In the preceding paper we discussed the influences of the chirality of a phosphorus atom contained in a 2-oxo-1,3,2-oxazaphosphorinane ring on the stereoselectivity of the alkylation of an adjacent methylene carbanion. 1 In continuation of our study into the factors that influence the stereochemistry of the alkylation of phosphorus stabilised carbanions, we turned our attention to those carbanions adjacent to both an asymmetric phosphorus atom and an asymmetric carbon atom. Scheme 1 Reagents and conditions: a) BuLi, THF, -78 °C; b) MeI, -78 °C; c) TMSCl, -78 °C, 1 h; d) LDA, toluene, -78 °C; e) MeI, -78 °C to r.t.The role of a β-substituent on α-alkylation of diphenylphosphine oxides has been investigated by Warren who showed that silylation proceeds stereoselectively, whereas methylation was not selective (Scheme 1, a). 2 Denmark 3 and we 1 have shown that an asymmetric phosphorus atom significantly controls the stereoselectivity of the alkylation at the adjacent carbanion (Scheme 1, b). Although the role of an adjacent asymmetric carbon atom and an adjacent asymmetric phosphorus atom on the alkylation of methylene carbanions has been independently studied, this is the first report of the combined influences of the two asymmetric centers.For our study, we chose compounds 1a, 1 1b 4 and 1c, 4 prepared as reported elsewhere (Figure 1). Compound 1a, alkylation of which has been reported in the preceding paper, contains only one asymmetric phosphorus atom. Compounds 1b and 1c are diastereomerically pure compounds containing two stereocenters, one at the phosphorus atom and another at the β-carbon atom. Alkylations were carried out under similar conditions in toluene, at -78 °C using LDA as base (Scheme 2). 5 The anion was reacted with four different electrophiles: methyl iodide, allyl bromide, benzyl bromide and chlorotrimethylsilane (TMSCl). The results are shown below ( Table 1). The diastereomeric ratios were determined by 31 P NMR on crude reaction products and are expressed as that of the higher chemical shift isomer to the lower chemical shift isomer. The relative configuration of the major diastereomers was determined by NOE between the α-proton and the ring CH 2 's.Scheme 2 Reagents and conditions: a) LDA (1.5 equiv), toluene, -78 °C, then E + .

show abstract

Asymmetric Induction by Chiral Phosphorus

Cited by 6 publications

References 1 publication

Asymmetric nucleophilic addition to vinylphosphonamidates (Part IV)

Asymmetric nucleophilic addition to vinylphosphonamidates (Part IV)

Palladium‐ and Nickel‐Catalyzed Coupling Reactions of α‐Bromoalkenylphosphonates with Arylboronic Acids and Lithium Alkenylborates

Alkylation of Asymmetric Phosphonamidates (Part II)

Contact Info

Product

Resources

About