| Budget Amount *help |
¥15,200,000 (Direct Cost: ¥15,200,000)
Fiscal Year 2003: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥11,600,000 (Direct Cost: ¥11,600,000)
|
|---|
| Research Abstract |
General principles for generating alkylidene-and vinylidene-complexes from alkynes were found to apply ~to transition metal-catalyzed reactions. Intramolecular cyclization or migration in pre-formed π-alkyne complexes occurs to give an alkylidene-or a vinylidene-complex.
We have demonstrated that 2-pyranylidene-chromium complexes were prepared from (β-ethynyl-α,β-unsaturated esters and amides in the presence of triethylamine. A chromium-vinylidene complex is a key intermediate in the reaction. Application of this protocol to cis-l-ethynyl-2-acylcyclopropane provided a new catalytic aromatization reaction leading to o-substituted phenol via cyclopropylvinylidenes. In sharp contrast, the reaction of β-ethynyl-α,β-unsaturated ketones with M(CO)_5(THF) (M=Cr, W) gave, (2-furyl)carbene complexes selectively via nucleophilic attack of a carbonyl oxygen to a π-alkyne complex. This (2-furyl)carbene complex formation has been nicely applied to catalytic reactions using β-ethynyl-α,β-unsaturated
… More
ketones, in which cyclopropanation of alkenes, carbene transfer reactions with heteroatoms, and insertion reactions with hydrocarbons have, been demonstrated. Heteroaromatic ring-substituted carbene species, i.e. (2-pyrrolyl)carbenoids were also prepared from the corresponding β-ethynyl-α,β-unsaturated imino compounds.
Application to propargylic carboxylates has provided new access to vinylcarbenoids of transition metals. Thus, the nucleophilic attack of a carbonyl oxygen to an internal carbon in π-complexes of propargylic substrates followed by bond cleavage at propargylic position gave vinylcarbene complexes. A wide range of transition metal complexes is effective for the purpose. Particularly, a [RuCl_2(CO)_3]_2 complex as a catalyst can promote the intermolecular cyclopropanation of alkenes using propargylic carboxylates as precursors of vinylcarbenoids. The reaction of conjugated dienes with propargylic substrates afforded seven-membered rings via cyclopropanation and subsequent [3,3]sigmatropic rearrangement. Less
|
