A Convenient Method for the Preparation of (Z)-α,β-Unsaturated Carbonyl Compounds

Pyrrolidine-Mediated Direct Preparation of (E)-Monoarylidene Derivatives of Homo- and Heterocyclic Ketones with Various Aldehydes

“…When other catalysts such as piperidine, Et 3 N, DIPEA, methyl glycinate, pyridine, proline and proline derivatives were screened, no better result was obtained (Table 1, entries 3-9). Methyl glycinate (1e), a primary amine, was employed as a catalyst too, and the monocondensation product 4a was obtained in 22% yield (Table 1, Proline, a prominent catalyst, had been used previously in aldol reactions between cyclic ketones and aldehydes, but when proline was used in this reaction, no product was detected, and not even the aldol product was detected ( [10][11][12][13][14][15][16]. Although the reaction solvents influenced the rate of the reaction, they did not affect the formation of (E)-4a as single product during the course of reaction, regardless of the protic or aprotic nature of the solvent.…”

“…Thus, the synthesis of these compounds has attracted increasing attention from chemists, biochemists and pharmacologists. So far, several strategies are reported for the preparation of these compounds, which are accomplished by various methods such as condensation, oxidation, elimination, acylation, and insertion of carbon monoxide, among others [7][8][9][10][11][12][13][14][15]. In connection with a project in our laboratory, we required mono-2-arylidene derivatives of ketones, particularly of piperidone.…”

“…Data were reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartlet, m = multiplet), coupling constants (Hz), integration. 13 C-NMR data were collected at 100 or 150 MHz with complete proton decoupling. Chemical shifts were reported in ppm from tetramethylsilane with the solvent (CDCl 3 ) resonance as internal standard.…”

Stereoselective Synthesis of Highly Substituted Tetrahydrofurans through Diverted Carbene OH Insertion Reaction

“…Diazo compound 11 which possesses a C-H bond α-to the diazo group gave tetrahydrofuran 21 in moderate yield due to competing 1,2-hydrogen shift. [14] When no α-C-H bond is present, as in diazo compound 12, an excellent yield (91%) of spiro-tetrahydrofuran 22 was obtained. Additionally, cyclic diazo compound 13 gave spiro compound 23 in good yield (77%), but only under rhodium catalysis.…”

Compostos alfa-diazo carbonílicos: uma estratégia atraente para a síntese orgânica

“…Um outro método também muito versátil para produzir α-diazoésteres envolve a benzoilação de ésteres em meio bási-co 13 . No exemplo apresentado no esquema 6, os produtos de condensação 25a e 25b reagem com o regente de transferência de diazo e DBU, formando a-diazo ésteres (26a-b) em bons rendimentos (Esquema 6).…”