Propargyl Ethylmalonates as Useful Building Blocks for the Preparation of Functionalized Butenolides

The Aminopalladation/Reductive Elimination Domino Reaction in the Construction of Functionalized Indole Rings

“…[25] Scheme 14 Scheme 15 The reaction most probably proceeds through an N-alkylation step that is followed by a cyclization step, the mechanism of which should be similar to that proposed for related base-catalyzed cyclization reactions of alkynes that we have recently investigated. [26,27] …”

“…[23] Use of conditions similar to those reported for the preparation of 2,3-disubstituted indoles [11] (Scheme 11a) and 2-unsubstituted 3-arylin- Scheme 11 doles [19] (Scheme 11b) met with failure, at least with our model system. The N-alkyl derivative 10 Ϫ generated by a competitive base-catalyzed nucleophilic substitution process Ϫ was isolated as the main or the sole reaction product.…”

An Electrochemical Alternative Approach to the Cyclization of Alkynes Bearing Proximate Malonyl Moieties

“…It is worth noting that this new electrochemical approach has the additional advantage of the milder reaction conditions. Unlike the previously developed base-promoted cyclization reaction of propargyl ethylmalonates 1, [8] the current cyclization reaction can be carried out at room temperature. Only with 1j did the cyclization only occur in MeCN at reflux, because of its poor solubility at room temperature in MeCN.…”

“…Only the most significant IR absorptions are given. The alkynes 1j, [8] 2a-b [9] and 3a-b [10] were prepared as reported in the literature. Analytical data for 3-pyrrolin-2-ones 5a-b were describeL, 3.6 mmol), piperidine (0.326 mL, 3.3 mmol), Pd(OAc) 2 (0.013 g, 0.06 mmol) and PPh 3 (0.031 g, 0.12 mmol) were added to a solution of 1-ethynylcyclohexanol (0.372 g, 3.0 mmol) in DMF (4.0 mL).…”

“…This strategy has further advantages because of the easy coupling of terminal alkyne functionality with organic electrophiles, such as aryl halides or vinyl triflates, which generates molecular diversity in the substrates and consequently in the target heterocycles. [7] In particular, the regioselective 5-exo-dig base-promoted cyclization of alkynes 1 and 2, each bearing a proximate malonyl moiety (Scheme 1), allowed the preparation [ of butenolides [8] 4 and 3-pyrrolin-2-ones [9] 5, respectively, whereas the alkynes 3 underwent regioselective 6-exo-dig cyclization to give quinolones [10] 6.…”