Revisiting the 7‐Phospanorbornene Family: New P‐Alkyl Derivatives

Abstract

A series of 1‐alkyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxides were converted to the corresponding phosphole oxides that, by the Diels–Alder reaction with N‐maleimide derivatives or with another unit of phosphole oxide, yielded trapped phosphole oxides or phosphole oxide dimers, respectively, as new 7‐phosphanorbornene 7‐oxides. The stereostructures of three derivatives were evaluated by single crystal X‐ray analysis. The regio‐ and stereospecific dimerization was studied by B3LYP/6‐31G(d,p) quantum chemical calculations, whose results were in accord with syntheses. Novel mechanistic features were explored. The geometrical data obtained by single crystal X‐ray analysis validated the results of quantum chemical calculations, as the deviation was less than 3%.

Probing the Structural and Electronic Effects on the Origin of π-Facial Stereoselectivity in 1-Methylphosphole 1-Oxide Cycloadditions and Cyclodimerization

“…A number of Diels–Alder reactions have been studied using the B3LYP DFT functional and reported in the literature. 5,22,25 The calculated results were found to be in good agreement with the experimental observations, and other DFT functionals such as M06-2X also corroborated well with B3LYP results. 26 We have computed the activation free energies for the syn and anti endo isomers of Diels–Alder reactions of 1-methylphosphole 1-oxide with different dienophiles like 1-methylphosphole 1-oxide and N -methylmaleimide, which were experimentally examined by Kovács et al (Scheme 2).…”

“…The [4 + 2] cycloaddition of phosphole 1-oxide with N -phenyl- or N -methylmaleimide was also reported. 22…”

“…These studies primarily focused on rationalizing the formation of exo/endo products and regioselectivity of P(IV) derivatives of phospholes. 22…”

The Impact of Microwaves on Organophosphorus Chemistry

“…7‐Phosphanorbornene derivatives were also prepared in a 3‐step protocol, and were converted to 2,3‐oxaphosphabicyclo[2.2.2]octene derivatives via Bayer‐Villiger oxidation. The bridged P‐heterocycles, precursors for methaphosphonates were utilized in the MW‐assisted phosphorylation of alcohols (Scheme ) …”

Fragmentation-Related Phosphonylation of Nucleophiles Utilizing P-Alkyl 2,3-oxaphosphabicyclo[2.2.2]octene 3-oxide Precursors

“…We decided to revisit the Baeyer–Villiger oxidation of 7‐phosphanorbornenes and utilize the P‐alkyl derivatives described by us recently . We were interested in the stability of the P‐alkyl 2,3‐oxaphosphabicyclo[2.2.2]octene derivatives, and it was also a task to compare the reactivity of the two regioisomers.…”