/pdf/ring-opening-of-epoxides-by-pendant-silanols-3697otx1.pdf

Ring Opening of Epoxides by Pendant Silanols

Ring Opening of Aziridines by Pendant Silanols Allows for Preparations of (±)-Clavaminol H, (±)-Des-Acetyl-Clavaminol H, (±)-Dihydrosphingosine, and (±)-N-Hexanoyldihydrosphingosine.

A salen-based Ce-MOFs contained rich uncoordinated imine (−CH=N−) groups (termed as N-Ce-salen) has been synthesized by using solution-diffusion method. Furthermore, the as-synthesized N-Ce-salen MOFs served as a “metalloligand” could coordinate with Fe(III) ions forming a MOFs supported Fe(III) ions catalyst via a coordination assisted preparation strategy (named as [email protected]). The coordination between the uncoordinated imine (−CH=N−) and Fe(III) ions was characterized by 13C solid-state NMR, N 1s XPS, FT-IR and UV-Vis techniques. The developed [email protected] catalyst delivers excellent performance for ring-opening of epoxides with alcohols reaction in comparison with that Ce-salen MOFs (using the same organic linker) without containing uncoordinated imine groups supported Fe(III) catalyst (named as Fe/Ce-salen-IWI) prepared by classic incipient wetness impregnation (IWI) method. Various characterization techniques, e.g. XPS, TEM, HADDF-STEM, were employed to reveal the origin of enhanced performance of [email protected] catalyst for ring-opening of epoxides with alcohols. We anticipate that this coordination-assisted preparation strategy may provide a new avenue for synthesis of other highly efficient MOFs supported catalysts for other heterogeneous catalytic reactions. 

Robust salen-typed Ce-MOFs supported Fe(III) catalyst fabricated by metalloligand strategy for catalytic epoxides with alcohols

We demonstrate that di-tert-butylsilanols are competent nucleophiles for the intramolecular interception of palladium π-allyl species. In these reactions, allyl ethyl carbonates are the best precursors for the formation of palladium π-allyl intermediates, and [(Cinnamyl)PdCl]2/BINAP is superior to other Pd salt/ligand framework combinations. Our optimized protocol is compatible with a variety of silanol substrates. Importantly, the cyclization is perfectly stereospecific, proceeding via an anti-syn mechanism, which stands in contrast to reported analogous reactions of alcohols and phenols, known to proceed via an anti-anti mechanism. The alkenes in the product dioxasilinanes serve as blank slates for further functionalization.

Highly Stereospecific Cyclizations of Homoallylic Silanols.

Covalent Tethers for Precise Amino Alcohol Syntheses: Ring Opening of Epoxides by Pendant Sulfamates and Sulfamides.

We present protocols for the highly regioselective hydroxyselenylation and silanoxyselenylation of allylic silanols. N-(Phenylseleno)phthalimide acts as the selenylating agent for both transformations. Under basic conditions, hydroxyselenylation proceeds with >20:1 regioselectivity, and the products are valuable synthons for further transformations. We show that the silanol plays a critical role in maintaining the yield and regioselectivity of this reaction. Surprisingly, under acidic conditions, the hydroxyselenylation pathway is blocked, and products of a tethered silanoxyselenylation are exclusive. 

HLADKYKH Fedir Volodymyrovych

Papers

Ring Opening of Epoxides by Pendant Silanols

Hydroxyselenylation and Tethered Silanoxyselenylation of Allylic Silanols