Diastereoselectivity in the Reduction of α-Oxy- and α-Amino-Substituted Acyclic Ketones by Polymethylhydrosiloxane

Abstract

Diastereoselectivity in the reduction of alpha-alkoxy-, alpha-acyloxy-, and alpha-alkylamino-substituted ketones with polymethylhydrosiloxane (PMHS) in the presence of fluoride ion catalysis was investigated. High syn-selectivity was observed in the reduction of alpha-alkoxy, alpha-acyloxy, and alpha-dialkylamino ketones. Reduction of alpha-monoalkylamino ketone proceeded in anti-selective manner with moderate selectivity. The observed selectivity is explained based on Felkin-Anh and Cram-chelate models.

Highly Recyclable Fluoride for Enhanced Cascade Hydrosilylation–Cyclization of Levulinates to γ-Valerolactone at Low Temperatures

“…As a byproduct of the silicone industry and an attractive liquid H-donor, polymethylhydrosiloxane (PMHS) is insensitive to water/air, nontoxic to organisms, and inexpensive, which has drawn great attention in the ionic hydrogenation or hydrosilylation of unsaturated groups (e.g., CC, CO, and CN) catalyzed by metal hydrids, salts, or complexes. − Unfortunatedly, some practical drawbacks like poor catalyst reusability and the requirement of proton species or extra hydrolysis steps for the dissociation of Si–X (X = O, N, and S) bonds to liberate products are always encountered, especially for the selective hydrogenation of carbonyl compounds. , To the best of our knowledge, no effective approach has been reported to simplify the postprocess and further in situ couple the hydrosilylation with other reactions.…”

Mechanistic Insight into the Reduction of Tertiary Phosphine Oxides by Ti(OiPr)4/TMDS

“…Furthermore, worldwide demand for environmentally friendly chemical processes and products requires the use of safer reagents that reduce or eliminate the generation of dangerous and toxic byproducts and decrease the amount of waste produced . In recent years, the rediscovery of the reductive abilities of hydrosiloxanes when associated with some transition metal, Lewis acid, or fluoride based catalysts renewed the interest in using hydrosiloxane as the stoichiometric reductive agent . Indeed, hydrosiloxanes, in comparison to most of the conventional reagents, have many advantages, since they are commercially available, air- and moisture-stable, nonpyrophoric, and soluble in most organic solvents.…”

Diastereoselectivities in Reductions of α-Alkoxy Ketones Are Not Always Correlated to Chelation-Induced Rate Acceleration

“…The spectroscopic data are consistent with literature data. 28,29 IR (neat): 3458, 2980, 1451, 1026, 824 cm -1 .…”