Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent: Theoretical and experimental results

Rajendra K. Jangid; Neelima Gupta; Raj K. Bansal; Moritz Von Hopffgarten; Gernot Frenking

doi:10.1016/j.tetlet.2011.02.007

Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent: Theoretical and experimental results

Rajendra K. Jangid, Neelima Gupta, Raj K. Bansal, Moritz Von Hopffgarten, Gernot Frenking

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

Theoretical calculations at the DFT (B3LYP/6-31+G) level of the model Diels-Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with 1,3-butadiene in the presence of methylaluminium dichloride reveal that the co-ordination of organoaluminium reagent to the carbonyl oxygen increases the activation barrier compared to that for the uncomplexed 2-phosphaindolizine. On the other hand, co-ordination of the organoaluminium reagent to the σ², λ³ P atom lowers the activation barrier by ∼6 kcal mol^-1. 1-Methyl-2-phosphaindolizines having an electron-withdrawing group at the 3-position only undergo DA reaction with 2,3-dimethylbutadiene in the presence of the ethylaluminium dichloride catalyst in methylene chloride at a low temperature to afford [2+4] cycloadducts. The formation of an intermediate having the ethylaluminium reagent co-ordinated to σ², λ³ P atom has been detected by ³¹P NMR. The products have been characterized by ³¹P and ¹H NMR studies.

Original language	English
Pages (from-to)	1721-1724
Number of pages	4
Journal	Tetrahedron Letters
Volume	52
Issue number	14
DOIs	https://doi.org/10.1016/j.tetlet.2011.02.007
State	Published - 6 Apr 2011
Externally published	Yes

Keywords

2-Phosphaindolizines
Al NMR
Catalysis by alkylaluminium dichloride
DFT calculations
Diels-Alder reaction
H NMR
P NMR

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10.1016/j.tetlet.2011.02.007

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title = "Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent: Theoretical and experimental results",

abstract = "Theoretical calculations at the DFT (B3LYP/6-31+G) level of the model Diels-Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with 1,3-butadiene in the presence of methylaluminium dichloride reveal that the co-ordination of organoaluminium reagent to the carbonyl oxygen increases the activation barrier compared to that for the uncomplexed 2-phosphaindolizine. On the other hand, co-ordination of the organoaluminium reagent to the σ2, λ3 P atom lowers the activation barrier by ∼6 kcal mol-1. 1-Methyl-2-phosphaindolizines having an electron-withdrawing group at the 3-position only undergo DA reaction with 2,3-dimethylbutadiene in the presence of the ethylaluminium dichloride catalyst in methylene chloride at a low temperature to afford [2+4] cycloadducts. The formation of an intermediate having the ethylaluminium reagent co-ordinated to σ2, λ3 P atom has been detected by 31P NMR. The products have been characterized by 31P and 1H NMR studies.",

keywords = "2-Phosphaindolizines, Al NMR, Catalysis by alkylaluminium dichloride, DFT calculations, Diels-Alder reaction, H NMR, P NMR",

author = "Jangid, {Rajendra K.} and Neelima Gupta and Bansal, {Raj K.} and Hopffgarten, {Moritz Von} and Gernot Frenking",

year = "2011",

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doi = "10.1016/j.tetlet.2011.02.007",

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T1 - Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent

T2 - Theoretical and experimental results

AU - Jangid, Rajendra K.

AU - Gupta, Neelima

AU - Bansal, Raj K.

AU - Hopffgarten, Moritz Von

AU - Frenking, Gernot

PY - 2011/4/6

Y1 - 2011/4/6

N2 - Theoretical calculations at the DFT (B3LYP/6-31+G) level of the model Diels-Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with 1,3-butadiene in the presence of methylaluminium dichloride reveal that the co-ordination of organoaluminium reagent to the carbonyl oxygen increases the activation barrier compared to that for the uncomplexed 2-phosphaindolizine. On the other hand, co-ordination of the organoaluminium reagent to the σ2, λ3 P atom lowers the activation barrier by ∼6 kcal mol-1. 1-Methyl-2-phosphaindolizines having an electron-withdrawing group at the 3-position only undergo DA reaction with 2,3-dimethylbutadiene in the presence of the ethylaluminium dichloride catalyst in methylene chloride at a low temperature to afford [2+4] cycloadducts. The formation of an intermediate having the ethylaluminium reagent co-ordinated to σ2, λ3 P atom has been detected by 31P NMR. The products have been characterized by 31P and 1H NMR studies.

AB - Theoretical calculations at the DFT (B3LYP/6-31+G) level of the model Diels-Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with 1,3-butadiene in the presence of methylaluminium dichloride reveal that the co-ordination of organoaluminium reagent to the carbonyl oxygen increases the activation barrier compared to that for the uncomplexed 2-phosphaindolizine. On the other hand, co-ordination of the organoaluminium reagent to the σ2, λ3 P atom lowers the activation barrier by ∼6 kcal mol-1. 1-Methyl-2-phosphaindolizines having an electron-withdrawing group at the 3-position only undergo DA reaction with 2,3-dimethylbutadiene in the presence of the ethylaluminium dichloride catalyst in methylene chloride at a low temperature to afford [2+4] cycloadducts. The formation of an intermediate having the ethylaluminium reagent co-ordinated to σ2, λ3 P atom has been detected by 31P NMR. The products have been characterized by 31P and 1H NMR studies.

KW - 2-Phosphaindolizines

KW - Al NMR

KW - Catalysis by alkylaluminium dichloride

KW - DFT calculations

KW - Diels-Alder reaction

KW - H NMR

KW - P NMR

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Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent: Theoretical and experimental results

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