Diastereo- and regioselectivity in Diels–Alder reaction of [1,4,2]diazaphospholo[4,5-a]pyridines

Bansal, R. K.; Karaghiosoff, Konstantin; Gupta, Neelima; Gandhi, Neelam; Kumawat, Surendra K.

doi:10.1016/j.tet.2005.08.045

Cited by 20 publications

(11 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This difference in the reactivities was correlated qualitatively with FMO energies calculated with semiempirical PM3 method [47]. In one case cycloaddition with 2,3-dimethylbutadiene alone could be completed only after refluxing in chloroform for 24 days [72]. In one case cycloaddition with 2,3-dimethylbutadiene alone could be completed only after refluxing in chloroform for 24 days [72].…”

Section: [2+4] Cycloadditionsupporting

confidence: 53%

“…The observed stereo-and regioselectivities in the above cases (Scheme 33) have been rationalized on the basis of theoretical calculations at the DFT level (B3LYP/6-311++G**//B3LYP/6-311G**) [72]. We have also accomplished successfully [2+4] cycloadditions of thiazolo [3,2-d] [1,4,2]diazaphospholes and their 5,6-dihydro and benzo derivatives (Scheme 35).…”

Section: [2+4] Cycloadditionmentioning

confidence: 72%

See 1 more Smart Citation

Recent Advances in the Chemistry of Anellated Azaphospholes

Bansal¹,

Gupta²,

Kumawat

2007

COC

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: [2+4] Cycloadditionsupporting

confidence: 53%

Section: [2+4] Cycloadditionmentioning

confidence: 72%

Recent Advances in the Chemistry of Anellated Azaphospholes

Bansal¹,

Gupta²,

Kumawat

2007

COC

Self Cite

View full text Add to dashboard Cite

show abstract

“…The reaction with isoprene under these conditions afforded two regioisomers, 38 (R = H) and 38′ in the ratio 7:3 (Scheme 12). 34 The observed stereo-and regioselectivities have been rationalized on the basis of theoretical DFT calculations. 34 …”

Section: Account Syn Lettmentioning

confidence: 99%

“…34 The observed stereo-and regioselectivities have been rationalized on the basis of theoretical DFT calculations. 34 …”

Section: Account Syn Lettmentioning

confidence: 99%

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

Bansal

Kour

2015

Synlett

View full text Add to dashboard Cite

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.

show abstract

“…The DA reactions of thiazolo [3,2-d][1,4,2]diazaphospholes and their 5,6-dihydro-and benzo-derivatives and those of 1,3-azaphospholo [5,1-b]benzothiazole occur with complete endo stereoselectivity, and in the reaction with isoprene, 70-100% regioselectivity is observed [16]. [1,4,2]Diazaphospholo [4,5-a]pyridines follow a similar course in their DA reactions with 2,3-dimethylbutadiene and with isoprene, 80% regioselectivity being observed in the latter case [17].…”

Section: Introductionmentioning

confidence: 98%