Theoretical Study of the Cycloaddition Reaction of a Tungsten‐Containing Carbonyl Ylide

Abstract

The [3+2] cycloaddition reaction of a tungsten-containing carbonyl ylide with methyl vinyl ether and the insertion reactions of the nonstabilized carbene complex intermediates produced have been investigated through the use of B3LYP density functional theory. The [3+2] cycloaddition reaction of the tungsten-containing carbonyl ylide has been proven to proceed concertedly, reversibly, and with high endo selectivity. The intermolecular Si-H insertion reactions of the carbene complex intermediates have been proven to be favored over the intramolecular C-H insertion, in good agreement with experimental results. Moreover, the kinetic endo/exo ratio of the [3+2] cycloaddition reaction has been shown to determine the endo/exo selectivity of the Si-H insertion products. In addition, secondary orbital interactions involving the benzene ring and the carbonyl ligand on the metal center have turned out to strongly influence the high endo selectivity of the [3+2] cycloaddition reaction with methyl vinyl ether.

Mechanism and Origin of Selectivity in Platinum(II)‐Catalyzed Reactions of Acyclic γ,δ‐Ynones with Alkenes

“…Free energy profiles for [3+2] cycloadditions between ylide II and s ‐ trans methyl vinyl ether are shown in Figure . In accord with previous studies, [3+2] cycloadditions of ylide II with methyl vinyl ether are concerted but asynchronous, with absolute exo specificity. No endo ‐[3+2] adduct was found, and attempts to locate these adducts led to the endo ‐[4+2] adduct via TS6 a (see Figure ).…”

“…All computations used methyl vinyl ether in place of n ‐butyl vinyl ether. This smaller vinyl ether has been used in previous computational studies, and lead to good agreement with experimental data . Products exo ‐ P(c) , exo ‐ P′(c) and P(d) for the reaction of methyl vinyl ether correspond to exo ‐ P(a) , exo ‐ P′(a) and P(b) for n ‐butyl vinyl ether, respectively.…”

“…In a series of experimental and theoretical studies, Iwasawa and co‐workers reported the generation of tungsten‐containing carbonyl ylides and their cycloaddition reaction with alkenes . They found that this reaction proceeds through a concerted [3+2] cycloaddition pathway and explained the endo selectivity based on secondary orbital interactions . In subsequent work, Iwasawa and co‐workers reported novel platinum(II)‐catalyzed cycloadditions for the construction of an 8‐oxabicyclo[3.2.1]octane skeleton from acyclic γ,δ‐ynones with electron‐rich alkenes.…”

Mechanistic Investigation of Biocatalytic Heme Carbenoid Si−H Insertions

“…This Fe II feature is consistent with experimental reaction studies where the starting heme proteins were reduced to the catalytically competent ferrous form, and experimental spectroscopic studies using UV/Vis and NMR spectroscopies, X‐ray crystallography,− and XANES (directly sensitive to Fe oxidation state) which show that IPC has a dominant Fe II feature (i. e. closed‐shell singlet). The proposed concerted mechanism is reminiscent of that proposed for rhodium‐ and iridium‐carbenoid Si−H insertions and heme carbene cyclopropanations …”

“…Both a concerted mechanism as proposed for other metal carbenoid Si−H insertions and a stepwise radical mechanism reminiscent of heme‐enzyme catalyzed oxidation reactions were investigated for reaction 1 to explore the basic mechanism, with details in Supporting Information ( SI ) and key results discussed here.…”