An Efficient Procedure for the Preparation of (E)-α-Alkylidenecycloalkanones Mediated by a CeCl₃·7H₂O−NaI System. Novel Methodology for the Synthesis of (S)-(−)-Pulegone¹

Abstract

2-Alkylidenecycloalkanones are powerful synthons used as the key intermediates in many important syntheses. Because of their potential, a general method of preparation from readily available starting materials, under very mild conditions, was considered to be worthwhile. Cerium(III) chloride heptahydrate in combination with sodium iodide in refluxing acetonitrile promotes a regio- and stereoselective beta-elimination reaction to (E)-2-alkylidenecycloalkanones in 2-(1-hydroxyalkyl)cycloalkanones. The synthetic value of the present procedure is demonstrated by the synthesis of monoterpene (S)-(-)-pulegone (8) in its optically active form.

N‐Arenesulfonyl‐2‐aminomethylpyrrolidines $\rm{-}$ Novel Modular Ligands and Organocatalysts for Asymmetric Catalysis

“…N-Boc-(S)-prolinol [7] A solution of N-Boc-(S)-proline (4.94 g, 23 mmol) in THF (35 mL) was stirred under nitrogen and cooled to 0 8C, when BH 3 -DMS (4.38 mL, 46 mmol) was carefully added. The reaction mixture kept at 0 8C for an additional 5 h and then left to warm up overnight.…”

“…[7] Reduction of N-Boc-protected l-proline with borane-dimethyl sulfide smoothly generated the corresponding (S)-prolinol in 95% yield. Treating the protected prolinol with tosyl chloride resulted in the formation of the sulfonyl ester 6 in high yield.…”

Investigation of amino acid containing [FeFe] hydrogenase models concerning pendant base effects

“…One possible explanation for the decomposition is the presence of the free amino group, as the amino-function itself is able to coordinate to iron [33,34] and may form an instable assembly under these conditions. Accordingly, the ligand was protected (2) using di-tert-butyl dicarbonate [(Boc) 2 O] (Scheme 1) [35]. This protection should provide a fast and clean cleavage using trifluoroacetic acid, without reactions to the [Fe2S2] core [36].…”

Neodymium(III)‐Mediated Reformatsky‐Type Reactions of α‐Halo Ketones with Carbonyl Compounds

“…[13] Therein, treatment of α-bromo ketones with CeI 3 in THF at 23°C resulted in the formation of the corresponding enolates, which in the presence of an aldehyde electrophile gave α,β-unsaturated ketones through a formal aldol condensation [Equation (1)]. [14] Because there is only a limited number of reports on the use of other trivalent lanthanide salts for this type of carbon-carbon bond formation, [15] we envisioned that an improvement of this reaction might be accomplished by employing neodymium(III) salts instead of cerium triiodide. [16] (1)…”