Catalyst-Controlled Regiodivergent Synthesis of 1- and 3-Thiosugars with High Stereoselectivity and Chemoselectivity

Abstract

An effective regiodivergent synthesis toward 1-and 3thiosugars was achieved through palladium and cobalt catalysis, respectively. β-1-Thiosugars were obtained from 3,4-O-carbonateglycals and various thiols catalyzed by Pd 2 (dba) 3 in good yields with exclusive stereoselectivity and chemoselectivity, while only (3S)-3thiosugars were generated via Co(BF 4 ) 2 . Experiments and DFT calculations supported the proposed mechanism that the thiol moiety preferred to form a hydrogen bond with C4-oxygen from top-face in Pd conditions but thiols would coordinate with cobalt from bottom-face in Co conditions. The difference between Pd/Co−C1 and Pd/Co−C3 bond lengths of key intermediates provided further insights into the 1,3-regioselectivity.

Intermolecular Forces Dictate Vibrational Energy Transfer in Plasmonic–Molecule Systems

“…Therefore, with the motivation of exploring what molecular properties could be tuned to control the vibrational energy transfer from plasmonic materials to adsorbate molecules, we chose a series of aromatic thiols with different substituent groups as probe molecules. Aromatic thiols are known for their ability to form self-assembled monolayers (SAM) on metal surfaces, which ensures the surface selectivity of the SERS measurements. − They are also sulfur-containing precursors for production of pharmaceutical products and synthesis of thiosugars and thioglycosides. − However, we should point out that throughout the measurements, the studied molecules are not undergoing chemical reactions with the experimental conditions. This is to avoid the complexity brought by reactivity, which will change the distribution of probed molecules in the hot spots.…”

Conversion of Glycals to 2,3‐Di‐Substituted‐3‐Deoxy‐Glycals by N‐(Glycosyloxy) Acetamides‐assisted C‐2‐Alkenylation and C‐3‐Nucleophilic Substitution

“…Very recently, catalyst controlled selective synthesis of 3‐thiosugar enol ether from 3,4‐ O ‐carbonate‐glycals was explored by Yao et al in which different thiols were attached selectively at C3 position under cobalt catalysis (Scheme 1b) [9] . However, the protocol requires the presence of 3,4‐ cis hydroxyl, bulky group at C‐6 under harsh condition.…”

“…Very recently, catalyst controlled selective synthesis of 3thiosugar enol ether from 3,4-O-carbonate-glycals was explored by Yao et al in which different thiols were attached selectively at C3 position under cobalt catalysis (Scheme 1b). [9] However, the protocol requires the presence of 3,4-cis hydroxyl, bulky group at C-6 under harsh condition. We have developed a carbonylative chemistry for the synthesis of C-2 branched glycals from preactivated 2-iodoglycals and further treating these substrates under lewis acid with certain soft nucleophiles (thiols and Cl) results the formation of C-3 branched glycals (Scheme 1c).…”

Directed Dehydrogenative Copper‐Catalyzed C−H Thiolation in Pseudo‐Anomeric Position of Glycals using Thiol and Thiosugar Partners

“…[5] However, these two methods suffer from poor substrate scopes (mostly in terms of thiols) and use often harsh conditions. Recently, the use of metal-catalyzed reactions led to propose alternative accesses to thioglycosides via copper-, [6] nickel-, [7] or palladium [8] -catalyzed cross-couplings with halide partners [9] or glycals [10] (Scheme 1a).…”