4-Hydroxy-1,3λ3-azaphosphole

Märkl, Gottfried; Dorfmeister, G.

doi:10.1016/s0040-4039(00)95918-5

Cited by 18 publications

(2 citation statements)

References 4 publications

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“…In addition, a broad signal at δ 44.9 to 51.1 ppm (∆ν 1/2 5707 to 8834 Hz) and the absence of 31 P– 27 Al coupling may be due to exchange of the ligand [29]. 13 C NMR studies have been used extensively in the characterization of azaphospholes and their [2 + 4] cycloadducts due to their characteristic 13 C– 31 P coupling constants [30–32]. In view of this, the 13 C NMR spectrum of a representative product 8a was recorded.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Jangid¹,

Sogani²,

Gupta³

et al. 2013

Beilstein J. Org. Chem.

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SummaryThe Diels–Alder reaction of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy) dichloride complex with dimethylbutadiene was investigated experimentally and computationally. The >C=P– functionality of the complex reacts with 2,3-dimethylbutadiene with complete diastereoselectivity to afford [2 + 4] cycloadducts. Calculation of the model substrate, 3-methoxycarbonyl-1-methyl-2-phosphaindolizine-P-aluminium(O-menthoxy) dichloride (7a), at the DFT (B3LYP/6-31+G*) level reveals that the O-menthoxy moiety blocks the Re face of the >C=P– functionality, due to which the activation barrier of the Diels–Alder reaction of 7a with 1,3-butadiene, involving its attack from the Si face, is lower. It is found that in this case, the exo approach of the diene is slightly preferred over the endo approach.

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Section: Resultsmentioning

confidence: 99%

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Jangid¹,

Sogani²,

Gupta³

et al. 2013

Beilstein J. Org. Chem.

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“…Other early routes to more highly substituted derivatives involve O–P replacement reactions of oxazolium salts with P(SiMe 3 ) 3 , in analogy to the first phosphinine synthesis,17 conversions of muenchnones with phosphaalkenes containing suitable leaving groups,17 or direct [3+2] cycloadditions of muenchnones or nitrilimines with phosphaalkynes,18 and – last but not least – base‐induced condensation of Bn # ‐substituted (Bn # = p ‐O 2 N‐C 6 H 4 ‐CH 2 ‐) CH‐acidic ketene‐aminals p TolCH=CH(NR 2 )NBn # Ph with PCl 3 . 1,3‐Oxaphospholes and 1,3‐thiaphospholes have been obtained by analogous condensations with OBn # ‐ and SBn # ‐substituted ketene aminals,19 reactions of t BuC≡P with arylmethoxycarbene Cr(CO) 5 complexes, with α,α′‐diketo‐diazo compounds or with isomuenchnones formed from them,20 and with 1,3‐dithiolium‐4‐olates,17b,18a,21 respectively. All of these syntheses have previously been reviewed in detail and are mentioned here only briefly 4,5a,5b,9.…”

Section: Recent Syntheses and New Types Of Electron‐rich Heterophomentioning

confidence: 99%

Electron‐Rich Aromatic 1,3‐Heterophospholes – Recent Syntheses and Impact of High Electron Density at σ²P on the Reactivity

Heinicke

2015

Eur J Inorg Chem

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This account reviews recent syntheses, properties, and the reactivity of electron‐rich aromatic 1,3‐heterophospholes, with the focus on benzazaphospholes, but also with inclusion of 1,2,4‐diazaphospholes containing the N–C=P–C motif and related O‐ and S‐containing heterocycles. Effects of the high electron density at phosphorus, a consequence of the position of the lone‐pair donating nitrogen atom in conjugation with dicoordinated (σ2) phosphorus and of the absence of P–N bonds, are illuminated by comparison of selected properties and reactions with those of less electron‐rich heterophospholes and phosphinines. Particular features of the electron‐rich heterocycles are CH‐lithiations of the P=CH fragment by tBuLi without addition at the P=C double bond in polar media, occurrence of inverse addition besides normal addition in less polar solutions, P‐alkylation and catalytic P‐arylation, and – last but not least – the avoidance of σ‐coordination of non‐zerovalent d10 transition metals within the ring plane in favor of μ2‐P and/or tilted η1‐P coordination.

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2‐Phosphaindolizines

et al. 1991

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Pyridinium bromides 3 prepared by alkylation of 2-methyl-, 2-ethyl-, and 2-benzylpyridines 1 with methyl bromides 2 bearing an electron-withdrawing group (COPh, CN, C02Et, C6H4NO2) are condensed with PC1, in the presence of Et3N to give 2-phosphaindolizines 4. The 1-unsubstituted representatives 9 (prepared from 8) may undergo a substitution reaction at this position with an excess of PC13 1-and 2-phosphaindolizines are 1,3-azaphospholes with a pyridine ring a-annuAzaphospholes constitute a relatively recent group of fivemembered aromatic heterocycles'). Among these systems representatives with and without a nitrogen atom adjacent to the phosphorus atom in the ring may be distinguished. While the former can usually be prepared by a condensation reaction using PC1, or P(NMe2),, the latter (1,3-azaphospholes and 1,2,4-diazaphospholes) are obtained by condensation with phosphines or silylphosphines or by cycloaddition reactions. Thus, the monocyclic 1,3-azaphospholes as well as their benzo and pyrido derivatives B7-12) and D4) have been prepared. The latter may be viewed as 1 -phospha analogs of indolizines E.are not yet known. In this paper we report on their synthesis by means of a PC1, c~ndensationl~). This is the first example of a heterophosphole with carbon atoms on both sides of the two-coordinate phosphorus atom in the ring being formed in this way27). As the positions 1 and 2 of the indolizine ring are different in ~haracter'~) the phosphorus ring member in these positions and hence the systems D and C should differ characteristically, e.g. in their NMR spectra and in their reactivity. SynthesisThe PCI3 condensation of a suitable four-membered chain presents a facile route to heteropho~pholes'~). For the synthesis of 2-phosphaindolizines of type C 1,2-dialkylpyridilated to the 1,2 and 1,5 bond, respectively. The different types of annulation result in characteristic differences in charge distribution, 31P-NMR shift, and chemical behavior. 2-Phosphaindolizines 4 and 9 are stable in dry air and do not undergo alkylation. Compounds 9 hydrolyze to give zwitterionic ' (1-alkyl-2-pyridino)methylphosphinates 13. The phosphorus atom of a 2-phosphaindolizine can act as a ligand atom as shown by the example of a Cr(CO), complex.nium salts 3 offer themselves as the starting material. Their 2-methylene group is sufficiently reactive for a triethylarninemediated condensation; its deprotonation results in a stable enamine16'. In contrast, the 1-methylene group needs activation by an electron-withdrawing substituent R2. COPh, CN, C02Et, and C6H4N02-4 have been found to be effective for this purpose. The respective pyridinium salts 3 are readily obtained17-19) from 2-ethyl-or 2-benzylpyridine (1 a, c) and phenacyl bromide (2a), bromoacetonitrile (2 b), ethyl bromoacetate (2c), or 4-nitrobenzyl bromide (2d). For the condensation, equimolar amounts of 3 and PC1, are treated with a fourfold molar amount of Et3N in toluene at ambient temperature or preferably in acetonitrile at 0 -5°C. The reaction is usually complete within...

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4-Hydroxy-1,3λ3-azaphosphole

Cited by 18 publications

References 4 publications

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Electron‐Rich Aromatic 1,3‐Heterophospholes – Recent Syntheses and Impact of High Electron Density at σ²P on the Reactivity

2‐Phosphaindolizines

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4-Hydroxy-1,3λ3-azaphosphole

Cited by 18 publications

References 4 publications

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Electron‐Rich Aromatic 1,3‐Heterophospholes – Recent Syntheses and Impact of High Electron Density at σ2P on the Reactivity

2‐Phosphaindolizines

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Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

Electron‐Rich Aromatic 1,3‐Heterophospholes – Recent Syntheses and Impact of High Electron Density at σ²P on the Reactivity