White, James D. published the artcileIron catalyzed enantioselective sulfa-Michael addition: a four-step synthesis of the anti-asthma agent Montelukast, SDS of cas: 162515-68-6, the publication is Chemical Science (2014), 5(6), 2200-2204, database is CAplus.
A salen ligand based on a chiral cis-2,5-diaminobicyclo[2.2.2]octane scaffold forms an iron(iii) complex with ferric chloride which catalyzed asym. addition of thiols to α,β-unsaturated ketones under mild conditions. The reaction (sulfa-Michael addition) produces β-thioketones in excellent yield and high enantiomeric excess from a wide range of aliphatic and aromatic thiols using chalcones and other conjugated enones as Michael acceptors. With α-substituted α,β-unsaturated ketones as acceptors, the addition showed strong preference (typically >50 : 1) for the syn diastereomer over the anti product. An asym. synthesis of (R)-Montelukast, the sodium salt of which is the com. anti-asthma drug Singulair, was devised using conjugate addition of a thiol catalyzed by our iron(III)-salen complex to an α,β-unsaturated ketone synthesized in a four-component, one-pot tandem Michael-aldol condensation. The reaction sequence to (R)-Montelukast proceeded in 72% overall yield over four steps from com. available materials. A mechanism for our catalyzed asym. sulfa-Michael addition was advance which coordinates the enone acceptor to the metal center of the iron-salen complex in an open lower quadrant under the bicyclic scaffold, thereby exposing only the si face of the double bond to attack by the external nucleophilic thiol. Prior internal coordination of the thiol to the metal center of the complex is proposed based on spectroscopic and chem. evidence and leads to activation of the catalyst through a trans ligand effect.
Chemical Science published new progress about 162515-68-6. 162515-68-6 belongs to quinuclidine, auxiliary class Thiol,Carboxylic acid,Aliphatic cyclic hydrocarbon, name is 2-(1-(Mercaptomethyl)cyclopropyl)acetic acid, and the molecular formula is C9H20Cl2Si, SDS of cas: 162515-68-6.
Referemce:
https://en.wikipedia.org/wiki/Quinuclidine,
Quinuclidine | C7H13N | ChemSpider