Reactions of a Metallacyclobutene Complex with Alkenes

Abstract

The first productive reactions of a characterized metallacyclobutene complex with alkenes are reported. Thus, the metallacyclobutene complex (eta5-C5H5)(PPh3)Co[kappa2-(C,C)-C(SO2Ph) C(Si(CH3)3)CH(CO2CH2CH3)] (2) undergoes reaction with alkenes to give 1,4-diene complexes with a high degree of regio- and stereoselectivity. A mechanism is proposed in which the metallacyclobutene generates a cyclic vinylcarbene intermediate that undergoes [4 + 2]-cycloaddition reactions with activated alkenes. A model of the vinylcarbene intermediate has been examined using quantum mechanical methods.

Nickel-Catalyzed Domino Cross-Electrophile Coupling Dicarbofunctionalization Reaction To Afford Vinylcyclopropanes

“…This anticarbometallation reaction occurs via TS18 . Similar nucleophilic additions to the internal carbon of an allene have been identified in related transformations …”

Osmapyridine and Osmapyridinium from a Formal [4+2] Cycloaddition Reaction

“…[18] Very recently, the reaction between cobaltacyclobutene and alkene was first reported to give the 1,4-diene complexes. [19] This reaction involved the conversion of the cobaltacyclobutene to a cobalt vinylcarbene intermediate, which underwent a [4+2] cycloaddition reaction with the alkene. The route to 3 and 4 involves a formal [4+2] cycloaddition reaction between acetonitrile and the osmium hydrido alkenylcarbyne complex, which is used as the precursor of the 1-metalla-1,3-diene.…”

The Isolation of a Large Cyclopentadienylcobaltsulfide Cluster. The Synthesis and Crystal Structure of Octahedral closo-(η5-C5H5Co)5S

“…It appears that the sulfur present in 1 is derived from the phenyl sulfone in complex 2, although the small quantities of 1 do not allow us to rule out that traces of sulfur-containing impurities may have been present in the starting material. Mechanistically, the six-electron reduction of the sulfone to a terminal sulfido presents difficulty, though this transformation may be facilitated by a metal-mediated oxidation of free triphenylphospine to triphenylphosphine oxide and subsequent metal-mediated C-S bond cleavages [5][6][7][8][9].…”