6135-22-4Relevant academic research and scientific papers
Formation of benzocyclobutenes from substituted oxocycloocta-2,8-diene-1,2-dicarboxylates Dedicated to the memory of Professor Alan Roy Katritzky
Bezen?ek, Jure,Gro?elj, Uro?,Po?kaj, Marta,Svete, Jurij,Stanovnik, Branko
, p. 5705 - 5708 (2015/09/29)
Substituted benzocyclobutenes were isolated from the reaction of substituted oxocycloocta-2,8-diene-1,2-dicarboxylates with DMAD which were themselves formed by the microwave assisted [2+2] cycloaddition of cyclic enaminones to dimethyl acetylenedicarboxylate. The high pressure hydrogenation of (1E,2Z)-dimethyl 3-(dimethylamino)-7-oxocycloocta-2,8-diene-1,2-dicarboxylate gave oxabicyclo[3.3.1]non-3-ene-2,3-dicarboxylates, while use of low pressure hydrogenation resulted in only the carbonyl group being reduced to give the corresponding hydroxyl derivative which was proposed as an intermediate of the oxabicyclo[3.3.1]nonanes formed using high pressure hydrogenation.
Selectivity in β-Enamino Ketone Anion Generation and Alkylation
Chen, Yuhpyng Liang,Mariano, Patrick S.,Little, Garrick M.,O'Brien, Daniel,Huesmann, Peter L.
, p. 4643 - 4654 (2007/10/02)
The regioselectivity of anion generation from β-alkoxy- and β-(dialkylamino)-α,β-unsaturated ketones was probed by use of (13)C NMR spectroscopy and alkylation techniques.Results indicate that the kinetic anions of these systems can be formed selectively from the parent ketones by using excess lithium diisopropylamide as the base at -78 deg C and diethyl ether or tetrahydrofuran as the solvent.The kinetic anion in these systems is the one resulting from deprotonation at the α'-carbon.Alkylation occurs at this center in synthetically useful yields.Equilibration to produce the thermodynamically more stable extended γ-enolate anion occurs when less than 1 equiv of lithium diisopropylamide is present and at elevated temperatures (>-20 deg C).The rate of equilibration is sensitive to the solvent employed, occurring much more rapidly in tetrahydrofuran than in diethyl ether.A synthetically more practical method for formation and alkylation of the thermodynamic anions of β-(dialkylamino)-α,β-unsaturated ketones utilizes excess lithium bis(trimethylsilyl)amide as the base in tetrahydrofuran as the solvent at -78 deg C followed by quenching with the alkylating agent.Methods for regioselective generation of dianions from β-(alkylamino)-α,β-unsaturated ketones have been explored.Analysis of products produced by methylation suggest that the N,α'- and N,γ-dianions can be produced independently by use of the respective kinetic and thermodynamic anion-producing conditions described above.However, all attempts to identify these dianions by spectroscopic methods failed due to the exceedingly low solubilities of these substances in solvent systems compatible with the technique.Likewise, dialkylation or acyclation-alkylation of the N,γ-dianions, in attempts to develope one-step procedures for fused-bicyclic pyrrolidine synthesis, was unsuccessful.
