Catalytic asymmetric Michael/cyclization reaction of 3-isothiocyanato thiobutyrolactone: an approach to the construction of a library of bispiro[pyrazolone-thiobutyrolactone] skeletons

Abstract

Here, we demonstrate that the first example of 3 isothiocyanato thiobutyrolactone serving as an useful building block in Michael/cyclization reaction with alkylidene pyrazolones for the enantioselective construction of optically active...

Isothiocyanates: happy-go-lucky reagents in organic synthesis

“…Yang and Zhou's group developed an efficient green method for the synthesis of 5-amino-1,2,4-thiadiazoles (36) from amidine hydrochloride (34) and isothiocyanates (35). 22 The protocol avoids the use of any transition metal catalyst, or iodine for the construction of C-N bond.…”

“…Based on the control experiments and available literature reports, a plausible mechanism is proposed for this cyclisation. Initially, in the presence of TMEDA (N,N,N′,N′-tetramethylethylenediamine), benzamidine hydrochloride (34) reacts with isothiocyanate to form intermediate A. Organic & Biomolecular Chemistry Review lines. 23 This one-pot cyclisation of substituted sulfonamides is achieved with a wide functional group tolerance and excellent stereoselectivity.…”

“…The targeted bispiro[ pyrazolonethiobutyrolactone] (65) skeletons having three adjoining stereocenters were obtained in up to 90% yield, >20 : 1 dr and >99% ee (Scheme 26). 34 In 2021, the Retailleau group disclosed a DABCO-catalyzed three-component reaction of chalcones (66), isothiocyanates (67), and elemental sulfur to access thiazole-2-thiones (68) in excellent yields. 35 In this protocol, elemental sulfur serves as a sulfur source as well as an oxidant.…”

“…The targeted bispiro[pyrazolonethiobutyrolactone] ( 65 ) skeletons having three adjoining stereocenters were obtained in up to 90% yield, >20 : 1 dr and >99% ee (Scheme 26). 34…”