Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• years of development. The effort of our group to broaden possibilities to engage metal enolates in reactions with new electrophiles is described. The material is divided according to the organometallic reagent employed in the conjugate addition step, and thus to the particular metal enolate formed

• stereoselective methodologies have been published that demonstrate the Cu- or Ni-catalyzed conjugate addition of organozincs to α,β-unsaturated ketones 14 followed by the reaction of the metal enolate with a nitroolefin (20) (Table 1) [30][31][32][33]. These reactions were facilitated by different ligand families

• sequence, were isolated in moderate to good yields and with high enantiopurities. Continuing with other Rh-based catalysts, the group of Lautens has also studied the stereoselective conjugate addition of alkynyl species to α,β-unsaturated ketones with subsequent trapping of the metal enolate by aldol

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• . eThe reaction was carried out using RhCl(PPh3)3 in THF at rt. Detection of metal-enolate and proposed mechanism of intramolecular cyclization. Synthetic route towards chiral necic acid lactone (2S,3S,4R)-2j. Conditions: a) CH3SO2NH2, AD-mix-β, t-BuOH, H2O. b) SO3·Py, Et3N, DMSO, CH2Cl2. c) DMAP, CH2Cl2

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• using a silver-BINAP catalyst combination [25]. Later, the same group could successfully tune the catalytic system to control the regioselectivity in the addition of metal enolate to nitrosoarenes to achieve an α-hydroxyamination [26]. Since then, several groups have shown the use of metal-catalyzed

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• ; domino aldol; metal enolate; tetrahydropyran; Introduction Since its discovery in the late nineteenth century the aldol reaction has become one of the most powerful tools in the field of carbon–carbon bond formation [1][2][3][4][5]. It is widely used in the formation of many natural products [6][7][8][9

• benzaldehyde (3a: Ar = Ph) (Scheme 2). The enolate was generated from propiophenone by deprotonation with lithium diisopropylamide (LDA) at −40 °C in tetrahydrofuran (THF) and was subsequently reacted with 0.33 equivalents of MCl3 or 0.25 equivalents of MCl4, respectively. The resulting metal enolate was then

• analyzing the harmonic vibrational frequencies, using analytical second derivatives. To predict the energies plausibly, as recommended for organometallic compounds, single point calculations with M06 functional [52] were performed using the same basis sets (Scheme 6). Complexation of the metal enolate E