Reaction of o-oxazolinylphenyllithium with carbon monoxide. Carbonylative cyclization via an aroyllithium intermediate

Organobase-Catalyzed Umpolung of Amides: The Generation and Transfer of Carbamoyl Anion

A novel organobase-catalyzed umpolung reaction of amides was disclosed. This method provides an efficient method to generate and transfer carbamoyl anions. In this transformation, some of the inherent disadvantages of carbamoyl metal were avoided. The mechanistic analysis revealed that the reaction proceeds through polarity inversion of amide, and various carbamoyl anions were applied in the reaction. Moreover, a wide range of substrates was achieved with moderate to excellent yield.

Steric Influence on Reactions of Benzyl Potassium Species with CO

Reactions of benzyl potassium species with CO are shown to proceed via transient carbene-like intermediates that can undergo either dimerization or further CO propagation. In a sterically unhindered case, formal dimerization of the carbene is the dominant reaction pathway, as evidenced by the isolation of ((Ph3 SiO)(PhCH2 )C)2 2 and PhCH2 C(O)CH(OH)CH2 Ph 3. Reactions with increasingly sterically encumbered reagents show competitive reaction pathways involving intermolecular dimerization leading to species analogous to 2 and 3 and those containing newly-formed five-membered rings tBu2 C6 H2 (C(OSiR3 )C(OSiR3 )CH2 ) (R=Me 6, Ph 7). Even further encumbered reagents proceed to either dimerize or react with additional CO to give a ketene-like intermediates, thus affording a 7-membered tropolone derivative 14 or the dione (3,5-tBu2 C6 H3 )3 C6 H2 CH2 C(O))2 15.

Carbonylation of 1-lithiobutadiene with carbon monoxide followed by intramolecular acyllithiation of C═C double bond and intermolecular acylation with acid chloride: scope, applications, and mechanistic aspects

The carbonylation of a 1-lithio-1,3-butadiene derivative with CO gave rise to a butadienyl acyllithio intermediate, which underwent an immediate intramolecular acyllithiation of the C═C double bond, affording a lithio cyclopentadienyl enolate. The X-ray structural analysis of the enolate revealed a dimer connected with a "Li(2)O(2)" four-membered ring. Subsequent intermolecular acylation of this enolate with acid chlorides afforded β-keto-3-cyclopentenones, γ-keto-2-cyclopentenones, or cyclopentadienyl ester derivatives. The stereo- and regioselectivity of the in situ generated lithio cyclopentadienyl enolate with various acid chlorides was investigated and analyzed, showing that the formation of the above products was significantly dependent on both the substituents on the butadienyl skeleton and the bulkiness of acid chlorides.

1-Lithio-1,3-dienes as useful building blocks in organic synthesis

Both intermolecular reactivities toward C-O and C-N unsaturated substrates and intramolecular reactions of various 1-lithio-1,3-dienes are briefly summarized. Results reveal that intramolecular synergy between the alkenyllithium moiety and the butadienyl skeleton make 1-lithio-1,3-diene derivatives useful and unique as building blocks in organic synthesis. It is demonstrated that substitution patterns and the nature of the substituents on the butadienyl skeleton have remarkable effects on reaction pathways.

n-Butyllithium/N,N,N‘,N‘-Tetramethylethylenediamine-Mediated Ortholithiations of Aryl Oxazolines: Substrate-Dependent Mechanisms

n-Butyllithium/N,N,N',N'-tetramethylethylenediamine-mediated ortholithiations of aryloxazolines are described. Methyl substituents on the aryloxazoline and substituents at the meta position of the arenes (methoxy, oxazolinyl, and fluoro) influence the rates and the mechanisms. Monomer- and dimer-based reactions are implicated. Density functional calculations probe details of the mechanism and suggest the origins of cooperative effects in meta-substituted aryl oxazolines.

Acyl-lithiation of olefins: formation of cyclopentenones from 1-lithio-butadienes and CO

[reaction: see text] Intramolecular acyl-lithiation of C=C double bonds proceeds following carbonylation of 1-lithio-1,3-dienes with CO to afford 2- or 3-cyclopentenone derivatives in good to excellent yields after hydrolysis. Addition of electrophiles to the carbonylation reaction mixtures affords various multiply substituted cyclopentenones.