Synthesis of [1,2,4,3]Triazaphospholo[1,5-a]pyridines<sup>+</sup>

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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“…and 1,2-diaminopyridinium iodides,6 as well as to other heterocyclic imines such as thiazole, benzothiazole and oxazole 7. …”

mentioning

confidence: 99%

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

Bansal

Kour

2015

Synlett

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“…1,3-diaza-2-phosphaindolizines (20) [36] (Scheme 8). In this case the use of PCl 3 was not found to be satisfactory, either no reaction occurred or the yield was very poor (~10%) [36].…”

Section: Synthesis Of Anellated [123]diazaphospholesmentioning

confidence: 99%

“…However, phosphorus of the anellated diazaphospholes is more deshielded and its signal shifts to 184 to 270 [27][28][29][30]34,44]. The 31 P NMR chemical shifts of triazaphospholo[1,5-a]pyridines, having nitrogen atoms on both sides of the phosphorus atom are most downfield and lie at 265 to 270 [36]. 13 till 1993 are included in an earlier review [11].…”

Section: Nmr Studiesmentioning

confidence: 99%

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Recent Advances in the Chemistry of Anellated Azaphospholes

Bansal¹,

Gupta²,

Kumawat

2007

COC

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Azaphospholes are 6 aromatic heterocycles incorporating at least one 2 , 3 -phosphorus atom and one 3 , 3nitrogen atom. This review covers the synthesis, structural characterization, reactions and theoretical calculations of azaphospholes anellated to a six-or five-membered heterocyclic ring, reported during the last 10-12 years. Three synthetic methods, namely [4+1] cyclocondensation, [3+2] cyclocondensation and 1,5-electrocyclization make a variety of these phosphorus heterocycles available. The aromatic character of these compounds has been confirmed by carrying out density functional theory (DFT) calculations. Mainly 1 H, 13 C and 31 P NMR studies have been employed for the structural characterization. Almost all the functionalities present in the azaphosphole ring have been investigated and electrophilic substitution reactions of the 1-unsubstituted compounds and Diels-Alder reactions as well as 1,2-addition reactions to the >C=P-moiety have been accomplished successfully. The stereo-and regioselectivities observed in the Diels-Alder reactions have been explained on the basis of DFT calculations. Cheletropic cycloadducts formed from [4+1] cycloaddition of o-quinones on the 2 , 3 -P atom have been obtained. A variety of coordination compounds formed bycoordination of the 2 , 3 -P atom have been prepared.

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“…As such, chloromethyl dichlorophosphine ClCH 2 PCl 2 turned out to be useful, and also methylene bis(dichlorophosphine) CH 2 (PCl 2 ) 2 . Azaphospholes 36-39 were synthesized [106][107][108][109][110], including anellated ones for which the 2-phosphaindolizines 40 and their aza-analogs 41-43 stand as examples [94,[110][111][112][113][114].…”

Section: Alfred Schmidpetermentioning

confidence: 99%

Molecules that we made: An essay on phosphorus chemistry

Schmidpeter¹

1999

Heteroatom Chem.

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Synthesis of [1,2,4,3]Triazaphospholo[1,5-a]pyridines⁺

Cited by 17 publications

References 10 publications

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

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

Recent Advances in the Chemistry of Anellated Azaphospholes

Molecules that we made: An essay on phosphorus chemistry

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Synthesis of [1,2,4,3]Triazaphospholo[1,5-a]pyridines+

Cited by 17 publications

References 10 publications

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

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

Recent Advances in the Chemistry of Anellated Azaphospholes

Molecules that we made: An essay on phosphorus chemistry

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Product

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Synthesis of [1,2,4,3]Triazaphospholo[1,5-a]pyridines⁺