Theoretical exammation of the Diels–Alder reaction of 1,3-butadiene with cyclopentadiene and 2H-phosphole

Abstract

All Diels-Alder reactions between 1,3-butadiene and cyclopentadiene or 2H-phosphole have been examined at the MP4SDQJ6-3 lG*//HF/6-31G* level. There is remarkable similarity between the two systems. The thermodynamic product is the bicyclo[4.2.0]nonadiene while the kinetic product is the norbornene product. There is a slight kinetic preference for the endo addition and for the butadiene to be in the s-trans conformation. Except for the case where butadiene is the diene component and addition is endo, the reactions are concerted and synchronous. In these other two cases, the reaction is stepwise with a diradical intermediate.Key words: phosphole, Diels-Alder reaction, topological electron density analysis.RCsumC : On a CtudiC toutes les rkactions de Diels-Alder entre le buta-1,3-dikne et le cyclopentadikne ou le 2H-phosphole au niveau MP4SDQJ6-3 lG*NHF/6-3 lG*. I1 existe une similarit6 remarquable entre les deux systkmes. Le produit thermodynamique est le bicyclo[4.2.0]nonadikne alors que le produit cinCtique est le produit norbornkne. I1 y a une 1Cgkre prCf6rence cinCtique en faveur de I'addition etldo et pour que le butadikne soit dans la conformation s-trans. A l'exception du cas ou le butadikne agit comme butadikne et que I'addition est endo, toutes les rCactions sont concertCes et synchrones. Dans ces deux autres cas, la rCaction se fait par Ctape avec un intermkdiaire diradicalaire.Mots clPs : phosphole, rCaction de Diels-Alder, analyse topologique de la densit6 Clectronique.[Traduit par la rCdaction]

Density Functional Theory Study on Dimerizations of Phospholes

“…Among the chemistries of five-membered heterocyclic compounds, that of phospholes is rather limited compared with those of pyrrole, furan, and thiophene. , However, soon after the discovery and unambiguous characterization of parent and substituted analogues, , the chemistry of phosphole has gained momentum, with notable contributions from Mathey's group . Exploration of the structure, stability, aromaticity, and reactivity of phospholes is intrinsically interesting due to their unique nature and has generated meaningful interplay between theoretical and experimental studies. − Although both 1 H - and 2 H -phospholes were independently characterized, ,, 3 H -phosphole is still elusive and is available only in the benzo-fused form, denoted as 3 H -phosphaindene . Phospholes and their Diels−Alder adducts exhibit novel modes of binding with transition-metal fragments, and phosphametallocenes have useful catalytic applications in olefin polymerizations. − Phospholes containing transition-metal fragments were also found to have potential applications in homogeneous catalysis such as hydrogenation, carbonylation, and hydroformylation reactions as well as in asymmetric synthesis …”

Diels−Alder Reaction of an Ene−Phospha−Yne

“…Much progress has been made recently in the preparation of phosphaalkynes, and these species are now readily accessible − suggested that the phosphorus analogue (reaction 2) may be easier to observe. We report here a high-level ab initio calculation comparing the energetics of these two reactions.…”

“…Similarly, the structure of TS2 is in accord with previous studies, with the forming C···C distance a bit shorter than usual. The forming C···P distance of 2.514 Å is typical for pericyclic reactions. − …”

“…Previous studies of phosphaalkenes and phosphaalkynes involved in Diels−Alder reactions have indicated a reduction in the barrier by approximately 10 kcal mol -1 relative to the all-carbon case. − The C−P π-bond is much weaker than the C−C π-bond, which leads to its more reactive nature. However, in the previous cases examined, a cumulene is not the product as it is here.…”

Ab Initio Study of the Thio-Ene Reaction. 1. The Enophile Substituent Effect

“…Recently, significant effort has been made to explore the ene chemistry of thio-carbonyl compounds. Since we − have been interested in the pericyclic reactions of heteroatomic systems, we decided to explore the nature of the mechanism of this reaction. In this paper, we report ab initio calculations on the thio-ene reaction, exploring the effect of substitution of the enophile.…”