α-Thiosubstituted chiral imines/secondary enamines: their use in the asymmetric Michael reaction

Disulfide-based metal-free α-sulfanylation of ketones

“…6 Also, interesting results have been obtained by different research groups performing metal-free organocatalyzed procedures. 7 However, none of the methods can be considered widely versatile because of some limitation related to the commercial availability of the starting materials, 8 or in some cases, reaction conditions and yields are not easily scalable or limited to small scale reactions. 1 As a prosecution of our studies on the development of new metal-free synthetic strategies, involving the preparation and selective transformation of cyclobutane derivatives, 9 we paid attention to the synthesis of some aphenylthio-substituted cyclobutanones 10 such as 2, which has been used in many organic transformations.…”

Catalysis of the Michael Reaction and the Vinylogous Michael Reaction by Ferric Chloride Hexahydrate

“…40 Most successful, however, is the derivatization of the keto group of the b-oxo ester with an optically active primary amine to yield an enamine or an imine. 41,42 In our laboratory we have focused on the application of a-amino acid amides as chiral auxiliaries. According to a combinatorial strategy we have screened various enamine esters such as 15 (Scheme 10) in combination with different metal salts as catalysts.…”

Michael Reactions and Conjugate Additions

“…The auxiliary is introduced by Brönstedt-acid-catalyzed imine formation. If water is removed, for 99 [67], -thiophenyl ketones (46d) [68], tetrahydrofuranone (46f) [69] to tetrahydrothiafuranone (46g) derivatives [70]. The yields given refer to the threestep sequence from 46 to 50, which is often performed as a one-pot protocol.…”