A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• pericyclic reactions with the iminium ions and therefore do not follow Equation 1 [53]. Let us now consider the role of counterions, as the imidazolidinone catalyzed reactions of cinnamaldehyde with pyrrole were reported to proceed with high yields and enantioselectivities, when using trifluoroacetic acid as

• ether [81], had previously been synthesized and characterized (X-ray structure) by Seebach et al. [30], neat samples of the imidazolidinone-derived enamines 32c–32e became only recently available by TsOH-catalyzed condensation of phenylacetaldehyde with the corresponding imidazolidinones and column

• nucleophilicities of the imidazolidinone derived enamines, which are in line with the larger 13C NMR chemical shifts of C-2 in 32d (101.9 ppm) and 32e (102.9 ppm) compared to that of C-2 in 32a (97.4 ppm), are not only due to the electron-withdrawing effect of the additional heteroatoms in the heterocyclic rings

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• organocatalytic Diels–Alder reactions to build up a tricyclic system. Herein, an asymmetric induction up to 96% enantiomeric excess was obtained by the use of imidazolidinone catalysts. This approach can be utilized to construct the tricyclic system in numerous natural products, in particular the scaffold of

• , organocatalytic methods are especially attractive for the preparation of compounds that do not tolerate metal contamination, e.g., active pharmaceutical ingredients. MacMillan’s imidazolidinone-based organocatalysts are general catalysts for a variety of asymmetric transformations. The first highly

• enantioselective organocatalytic Diels–Alder reaction was reported by MacMillan in his pioneering work in 2000 [17]. The activated iminium ion, formed through condensation of imidazolidinone and an α,β-unsaturated aldehyde, underwent reactions with various dienes to yield [4 + 2]-cycloadducts in excellent yields

Identification and synthesis of impurities formed during sertindole preparation

• I. V. Sunil Kumar,
• G. S. R. Anjaneyulu and
• V. Hima Bindu

Beilstein J. Org. Chem. 2011, 7, 29–33, doi:10.3762/bjoc.7.5

• -fluorophenyl)-1H-indol-3-yl]-1-piperidinyl]ethyl]-2-imidazolidinone. Its literature synthesis (Scheme 1) [1][2][3][4][5] involves the copper catalyzed N-arylation of 5-chloroindole (11) with 4-fluorobromobenzene (12). The product, 5-chloro-1-(4-fluorophenyl)indole (13), on treatment with 4-piperidinone

• -chloroethyl)imidazolidinone (16) in the presence of a base gives sertindole (1). During the laboratory optimization of sertindole (1), many process related impurities were identified. The guidelines recommended by ICH state that the acceptable levels for a known and unknown compound (impurity) in the drug

• Discussion During the catalytic hydrogenation of indole 15, formation of 0.5–1.0% of the des-chloro indole 17 is observed; the level is reduced to less than 0.1% during its isolation and purification. It is necessary to remove the impurity at this stage because after condensation with imidazolidinone 16, it

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• imidazolidinone rings [42]. Finally, enantiopure 2-phenyltetrahydropyrimidine-4(1H)-ones were successfully synthesised via a chiral pool approach by condensing Cbz-L-Asn-OAll (8) with benzaldehyde dimethylacetal (Scheme 4). Compared to the respective cyclisation reaction starting from 3, complete conversion of 8