Catalytic Effect of Organoaluminium Chloride Reagents on the Dienophilic Reactivity of Indolizine and 2-Phosphaindolizine towards [2+4] Cycloaddition: A DFT Investigation

Gupta, Neelima; Jangid, Rajendra K.; Bansal, R. K.; Hopffgarten, Moritz von

doi:10.2174/2211544711201020093

Cited by 7 publications

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“…As reported recently, the DFT calculations reveal that the activation energy of the DA reaction is lowered only if the aluminium catalyst is coordinated to the phosphorus atom; when it is coordinated to the carbonyl oxygen atom, the activation energy barrier is rather high as compared to that for the DA reaction of the uncomplexed 2-phosphaindolizine [42]. Computational calculations also show that the conformation of 2-phosphaindolizine corresponding to the global minimum has phosphorous and carbonyl oxygen atoms in the antiperiplanar positions [35], thus reducing the possibility of chelate formation.…”

Section: Resultsmentioning

confidence: 97%

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: 97%

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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“…On computing the DA reaction of 2-phosphaindolizine complexed with AlCl 3 through the σ 2 ,λ 3 -P atom, with 1,3-butadiene, the activation barrier was lowered remarkably to only 22.57 kcal mol -1 (Scheme 8). 28 In this case, NBO studies locate a lone pair at C3, which enters into strong second-order perturbative interactions with the πN=C and πP=C orbitals ( Figure 7). …”

Section: Account Syn Lettmentioning

confidence: 99%

Section: Theoretical Investigation Of the Catalytic Effect Of Alcl 3 mentioning

confidence: 99%

“…We therefore investigated the effect of aluminum chloride (AlCl 3 ) and organo-aluminum chloride catalysts on the dienophilic reactivity of indolizine and 2-phosphaindolizine in the DA reactions with 1,3-butadiene theoretically at the B3LYP/6-31+G** level. 28 Unexpectedly, it was found that coordination of AlCl 3 with the oxygen atom of the carbonyl group of indolizine or 2-phosphaindolizine, instead of lowering the activation barrier, raised it further in comparison It is obvious that coordination of AlCl 3 with the carbonyl group makes the bridgehead nitrogen atom donate its lone pair more efficiently than in the uncomplexed indolizine or 2-phosphaindolizine, thus making the dienophilic moiety, >C=Z-(Z = CH or P) more electron-rich. The NBO calculations locate a lone pair at the carbon atom of the original >C=P-functionality, which enters into strong second-order perturbations with the πN=C and πC=O orbitals (Figure 6).…”

Section: Theoretical Investigation Of the Catalytic Effect Of Alcl 3 On The Dienophilic Reactivity Of >C=c< And >C=p-functionalities In Imentioning

confidence: 99%

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Diels–Alder Reactions with the >C=P– Functionality of Annelated Azaphospholes

Bansal

Kour

2015

Synlett

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The >C=P-functionality in annelated azaphospholes acts as a dienophile and undergoes Diels-Alder reactions with dienes. 1,3-Bis(alkoxycarbonyl)-2-phosphaindolizines react with dienes even in the absence of a catalyst; however, in the presence of an oxidizing agent such as sulfur or selenium, the reaction is much faster. 3-Alkoxycarbonyl-2-phosphaindolizines with an electron-withdrawing group exclusively at position 3 undergo the Diels-Alder reaction only in the presence of a Lewis acid. Density functional theory calculations reveal strong hyperconjugative interactions between the nitrogen lone pair and the >C=P-functionality of the 3-alkoxycarbonyl-2-phosphaindolizine, making it electron-rich. However, in 1,3-bis(alkoxycarbonyl)-2-phosphaindolizines, the ester group at the position 1 acts as a sink for the lone pair of electrons of nitrogen leaving the >C=P-functionality sufficiently electron-deficient to undergo the Diels-Alder reaction.

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“…Then, we explored the possibility of using a Lewis acid as catalyst to accomplish DA reaction with 3-(alkoxycarbonyl)-1-methyl-1,3-azaphospholo[5,1- a ]pyridines and computed the following model reactions at the DFT (B3LYP/6-31+G**) level ( Scheme 9 ) [ 37 ]. For studying the solvent effect, single point energy was computed using gas phase-optimized geometry with PCM solvation model.…”

Section: Reactions Responsementioning

confidence: 99%

Synergy between Experimental and Theoretical Results of Some Reactions of Annelated 1,3-Azaphospholes

Bansal

Kour

2018

Molecules

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Computational calculations have been used successfully to explain the reactivity of the >C=P- functionality in pyrido-annelated 1,3-azaphospholes. Theoretical investigation at the Density Functional Theory (DFT) level shows that the lone pair of the bridgehead nitrogen atoms is involved in extended conjugation, due to which electron density increases considerably in the five-membered azaphosphole ring. The electron density in the azaphosphole is further enhanced by the presence of an ester group at the 3-position making the >C=P- functionality electron-rich. Thus, 1,3-azaphospholo[5,1-a]pyridine, i.e., 2-phosphaindolizine having ester group at the 3-position only does not undergo Diels-Alder (DA) reaction with an electron rich diene, such as 2,3-dimethyl-1,3-butadiene (DMB). However, an ester group at 1-position acts as electron-sink, due to which transfer of the electron density to the >C=P- moiety is checked and DA reaction occurs across the >C=P- functionality. The coordination of the Lewis acid to the carbonyl group at the 3-position raises the activation barrier, while it is lowered remarkably when it is coordinated to the P atom. Furthermore, the attack of 1,3-butadiene on the Si face of the P-coordinated (o-menthoxy)aluminum dichloride complex is a lower activation energy path. Fukui functions could be used to explain relative reactivities of indolizine and 2-phosphaindolizine towards electrophilic substitution reactions.

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Catalytic Effect of Organoaluminium Chloride Reagents on the Dienophilic Reactivity of Indolizine and 2-Phosphaindolizine towards [2+4] Cycloaddition: A DFT Investigation

Cited by 7 publications

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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

Diels–Alder Reactions with the >C=P– Functionality of Annelated Azaphospholes

Synergy between Experimental and Theoretical Results of Some Reactions of Annelated 1,3-Azaphospholes

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Catalytic Effect of Organoaluminium Chloride Reagents on the Dienophilic Reactivity of Indolizine and 2-Phosphaindolizine towards [2+4] Cycloaddition: A DFT Investigation

Cited by 7 publications

References 0 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

Diels–Alder Reactions with the >C=P– Functionality of Annelated Azaphospholes

Synergy between Experimental and Theoretical Results of Some Reactions of Annelated 1,3-Azaphospholes

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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