Organocatalytic asymmetric thio-Michael addition of arylmethyl mercaptans to cyclic enones by a primary amino acid

Abstract

A simple primary amino acid was found to be an efficient catalyst for thio-Michael addition of benzyl mercaptan to cyclic enones.Leave this area blank for abstract info.

Primary Amino Acid Lithium Salt-Catalyzed Asymmetric Michael Addition of Carbon Nucleophiles to Enones

“…Therefore, cyclohexane was chosen as a solvent for further investigations. 100 72 9 2 MeOH 100 62 4 3 MeCN 11 11 59 4 AcOEt 24 24 68 5 THF 27 22 68 6 CH 2 Cl 2 41 28 68 7 Toluene 60 45 65 8 Cyclohexane 94 69 70 a The reaction was carried out with 2a (0.6 mol), 3a (0.5 mmol) and 1a (0.15 mmol) in a solvent (1 mL) at 25 °C for 72 h; We then synthesized various siloxy amino acids and their alkali metal salts from L-serine, L-threonine (Thr) and L-tyrosine (Tyr) to perform a catalyst screen in cyclohexane (Table 2) [33][34][35][36][37][38][39][40]. Since L-serine derived catalyst 1a gave better results in both yield and enantioselectivity of 4a than did Thr(O-TBS)-OLi (1b) and Tyr(O-TBS)-OLi (1c), L-serine was selected as a basic amino acid and used for further modification of the catalyst ( Table 2, entries 1-3).…”

Sequential Ytterbium(III) Triflate Catalyzed One‐Pot Three‐Component Thia‐Michael Addition

“…3‐[(4‐Methoxybenzyl)thio]cyclohexanone (3 a) : To a solution of ( S )‐(4‐Methoxybenzyl) ethanethioate (100 mg, 0.51mmol) in MeOH (0.1 M) was added Yb(OTf) 3 (5 mol%) and cyclohex‐2‐enone (2.00 equiv), and the resulting mixture was stirred at 70 o C under nitrogen for 9 h. Upon completion of the reaction, the mixture was extracted with ethyl acetate (3x), and the combined organic phases were washed with brine, dried with MgSO 4 and filtered. The product was then purified by column chromatography (hexane/EtOAc=10:1) to give 3 a (110 mg, 86 % yield) as a colorless oil.…”

Asymmetric Organocatalytic Reactions of α,β-Unsaturated Cyclic Ketones

“…Unfortunately, Mukaiyama [64], Deng [70], and Shimizu [74], reported 1% ee (entry 1, Table 4) 21% (entry 4, Table 4) and 0% ee (entry 7, Table 4) respectively for the reaction of benzylmercaptan with cyclohex-2-en-1-one. Very recently, however, the addition of arylmethylmercaptans to cyclic enones has been successfully accomplished by a simple and commercially available catalyst: S-triphenylmethyl-L-cysteine (entry 9, Table 4) [76].…”