Efficient synthesis of β-enaminoesters via highly stereoselective Reformatsky reaction with disubstituted formamides as novel electrophiles

Accessing N-Stereogenicity through a Double Aza-Michael Reaction: Mechanistic Insights

Further development of the chemistry and applications of chiral compounds that possess configurationally stable stereogenic nitrogen atoms is hampered by the lack of efficient strategies to access such compounds in an enantiomerically pure form. Esters of propiolic acid and chiral alcohols were evaluated as cheap and readily available Michael acceptors in a diastereoselective synthesis of N-stereogenic compounds by means of a double aza-Michael conjugate addition. Diastereomeric ratios of up to 74:26 and high yields were achieved with (-)-menthyl propiolate as a substrate. Furthermore, a detailed mechanistic investigation was undertaken to shed some light on the course of this domino transformation. Kinetic studies revealed that the protic-solvent additive acts as a Brønsted acid and activates the ester toward the initial attack of the tetrahydrodiazocine partner. Conversely, acidic conditions proved unfavorable during the final cyclization step that provides the product.

Direct condensation of functionalized sp3 carbons with formanilides for enamine synthesis using an in situ generated HMDS amide catalyst

Functionalized enamines, including β-enaminoesters were synthesized using in situ generated HMDS amide bases via the combination of aminosilanes and fluoride salts.

Dynamic 1H NMR study around the carbon-carbon single bond and partial carbon-carbon double bond in the two particular phosphorus ylides and in an enaminoester

Herein, a series of separate dynamic (1)H NMR effects are reported at different temperatures within a particular enaminoester involving a phenanthridine. These effects are attributed to restricted rotation around the two single bonds such as carbon-carbon (H(a)-C-<arrow curve left)>C-H(b)) and nitrogen-carbon (NC<arrow curve left)>COOCH(3)). Activation energies (E(a)) for these interconversion processes in their rotational isomers are equal to 20 and 20 ± 1 kJ mol(-1), respectively. In addition, three dynamic (1)H NMR effects are investigated at different temperatures for a particular phosphorus ylide involving a 2-indolinone around the carbon-carbon single bond (H-C-<arrow curve left)>C-PPh(3)) within the two Z- and E-rotational isomers and partial carbon-carbon double bond (OCH(3)-C=<arrow curve right)>C-PPh(3)). Activation energies (E(a)) for these interconversion processes in rotational isomers are equal to 53, 63 and 73 ± 1 kJ mol(-1) , respectively. This behavior was also observed for other phosphorus ylide containing 2-mercaptobenzoxazole around the carbon-carbon single bond and partial carbon-carbon double bond with their relevant activation energies containing 13, 10 and 75 ± 1 kJ mol(-1), respectively.

3-Dimethyl-amino-1-(4-methyl-phen-yl)prop-2-en-1-one

In the title compound, C₁₂H₁₅NO, the C=C and C=O functional groups and the benzene ring are involved in an extended conjugated system. The mol­ecules are essentially planar with a maximal deviation from planarity for the non-H atoms of 0.062 (2) Å.