Diastereoselective thiol conjugate addition on δ-alkylated-γ-silylated-α,β-unsaturated-δ-lactones

Abstract

The silicon atom at the γ position of α-pyrone 1a plays a dramatic role in directing thiol conjugate additions in a diastereoselective way. We describe here a stereoselective access to γ-silylated-β-thio-δ-lactones.

Covalent Modifiers: A Chemical Perspective on the Reactivity of α,β-Unsaturated Carbonyls with Thiols via Hetero-Michael Addition Reactions

“… Goniothalamin derivative 150 and lactone 151 undergo a highly diastereoselective thiol addition, where the thiol adds anti to the trifluoromethyl or chloromethylene groups, giving adducts 152 or 153 in 86 or 92% yields, respectively . Lactone 154 , containing a bulky tert -butyl dimethylsilyl group adjacent to the Michael acceptor, required heating to 70 °C to effect thiol addition and thiols added anti to the silyl group to afford thiol adducts 155 – 157 ; bulkier thiols such as tert -butyl thiol and electron poor p -nitrothiophenol failed to react with 154 , demonstrating that the electronic and steric nature of the thiol also impacts the Michael addition reaction …”

Facile Synthesis of Functionalized Lactones and Organocatalytic Ring-Opening Polymerization

“…The conjugate addition of benzyl mercaptan to 5,6-dihydro-2H-pyran-2-one (DHP) was performed in the presence of triethyl amine at 80 °C. 22 BMVL was obtained in high yield (76%) as an odorless solid product. The ethylene-glycol functionalized monomers were prepared analogously by addition of either 2-(2-methoxyethoxy)ethanethiol or 1mercapto-3,6,9,12-tetraoxotridecane 26 to DHP to generate the substituted valerolactones EG 2 MVL (54% yield) or EG 4 MVL (44% yield), respectively (Figure 1).…”

“…The synthesis and ring-opening polymerization of functionalized lactones has proven to be a particular powerful strategy for generating functionalized polyesters, notwithstanding the often cumbersome and multistep syntheses required to prepare these monomers. ,,,,− Herein, we report a mild and facile method for generating functional lactones by a one-step Michael addition − of thiol compounds to the α,β-unsaturated valerolactone 5,6-dihydro-2 H -pyran-2-one (Figure ). While the conjugate addition of thiols to α,β-unsaturated lactones is known, − its application for the synthesis of functionalized valerolactones is a novel strategy for generating polymerizable lactones.…”

“…The conjugate addition of benzyl mercaptan to 5,6-dihydro-2 H -pyran-2-one (DHP) was performed in the presence of triethyl amine at 80 °C . BMVL was obtained in high yield (76%) as an odorless solid product.…”

Reactivity of silylated vinyloxiranes and silyl butene diols with palladium(0)

“…These highly functionalized lactones are efficient Michael acceptors that undergo conjugated additions and further electrophilic trapping with a high diastereoselectivity. When the electrophile is prochiral like the benzaldehyde, there is even an extracyclic stereogenic carbon atom whose configuration is controlled in the process of the trapping [33,34] (Scheme 10).…”