Stereoselective Synthesis of Thiochroman-4-ones by Ring Transformation of Chiral 5-Ylidene-1,3-dioxan-4-ones with 2-Bromothiophenol via Bromo−Lithium Exchange

Abstract

The reaction of (E)-or (Z)-5-ylidene-1,3-dioxan-4-one (1) and 2-bromothiophenol, followed by bromo-lithium exchange with nBuLi, provides a new access to optically active thiochroman-4-ones 4 and 5. Stereoselective conjugate addition occurs in the first step and the resulting 5-(1-phenylsulfanylalkyl)-1,3-dioxan-4-ones 2 and 3 undergo ring transformation to thiochroman-4-ones by attack of the lithiated phenyl

Development of Conjugate Addition of Lithium Dialkylcuprates to Thiochromones: Synthesis of 2-Alkylthiochroman-4-ones and Additional Synthetic Applications

“…HRMS data for compounds 4Aa , 4Ba – 4Ja , 5 , 7 , and 8 were analyzed by TOF MS. Compounds 4Ab – Ac , 4Ad – Af , and 6 have been fully characterized and reported [ 39 , 43 , 48 , 67 ].…”

“…Although some synthetic approaches to thiochroman-4-ones, thioflavone, and thiochromones have been reported in literature [ 28 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ], research on efficient synthesis of 2-substituted thiochroman-4-ones is an underexplored area when compared to O-containing counterparts. Synthetic approaches to 2-substituted thiochroman-4-ones utilizing Friedel-Crafts acylation of thiopropanoic acid [ 56 ], hydrogenation of thiochromones [ 57 , 58 , 59 ], and intramolecular thio-Michael addition [ 60 , 61 , 62 , 63 , 64 , 65 , 66 ] have been reported.…”

Synthetic Approaches to 2‐Alkylthiochroman‐4‐ones and Thioflavanones

“…The resulting 5‐(1‐phenylsulfanylalkyl)‐1,3‐dioxan‐4‐ones underwent ring transformation to thiochroman‐4‐ones by attack of the o ‐lithiated phenyl ring to the carbonyl carbon atom of dioxanone, cleaving off pivalaldehyde to give the chiral 2‐alkylthiochroman‐4‐ones ( 38 ) (Scheme 18). 34 …”

The Catalytic Asymmetric Construction of Trifluoromethylated Quaternary Carbon-Containing Thiochromans

“…To achieve this, the catalytic enantioselective sulfa-Michael cascade reaction is the most effective and wildly used strategy by many synthetic researchers. [39][40][41][42][43][44][45] In keeping with our interest in constructing trifluoromethylated chiral heterocyclic framework, 46 we disclose herein a squaramidecatalyzed [47][48][49][50][51][52][53] Michael-aldol reaction for the asymmetrical synthesis of thiochromans bearing three stereogenic carbon centers.…”