Highly Diastereoselective Chelation-Controlled 1,3-anti-Allylation of (S)-3-(Methoxymethyl)hexanal Enabled by Hydrate of Scandium Triflate

En route to the total synthesis of (+)-Neopeltolide, we explored Lewis acid-assisted diastereoselective allylation of MOM-protected 3-hydroxylhexanal with β-(2,2-diethoxyethyl)-substituted (allyl)tributylstannane. The hydrated form of scandium triflate was found to be essential for attaining high 1,3-anti-diastereoselectivity (d.r. 94:6), while the use of anhydrous catalyst resulted in a modest diastereocontrol (d.r. 76:24). The preferred 1,3-anti-selectivity in this transformation can be rationalized in the framework of the Reetz chelate model of asymmetric induction. The 1,3-anti-configuration of the product was confirmed by its conversion into the known C7-C16 building block of (+)-Neopeltolide. We also report an improved protocol for the synthesis of β-(2,2-diethoxyethyl)-substituted (allyl)tributylstannane, which can be utilized as a cost-efficient bipolar isoprenoid-type C5-building block in the synthesis of natural compounds.

Electrochemical methods for synthesis of organoelement compounds and functional materials

The new efficient and environmentally safe methods for preparation of various classes of organic and organoelement compounds, including organonickel sigma-complexes and organophosphorus compounds bearing P–C bonds have been created using the electrochemical methods. The synthetic application of the elaborated techniques towards the process of formation of new carbon-carbon, carbon-metal and carbon-phosphorus bonds are discussed. The mechanisms of the proposed processes and the nature of the formed in the overall electrochemical process intermediates are disclosed. The elaborated methods operated in the principals of “green chemistry” can be considered as an efficient alternative to some classical methods for preparation of active catalysts, biologically active molecules and new polynuclear complexes displaying practically useful properties.