Selective O-Acylation of Enol Silyl Ethers with Acyl Fluorides Catalyzed by Fluoride Ions Derived from Potassium Fluoride and 18-Crown-6.

The fluoride ion-catalyzed selective O-acylation of enol silyl ethers with acyl fluorides using KF and 18-Crown-6 is described herein. This catalytic system facilitated the practical and facile reaction of a variety of enol silyl ethers derived from aromatic/aliphatic ketones and aldehydes with acyl fluorides to afford useful and valuable enol esters.

Photoinduced Intramolecular Cyclization of Acylsilanes Bearing a Boronate Moiety: Construction of a Highly Strained Fused Bicyclo[3.3.0]octane Skeleton.

A reliable strategy for the construction of -fused bicyclo[.3.0] skeletons was explored by utilizing photoinduced cyclization of acylsilanes bearing a boronate.

Generation of (amino)(boryloxy)carbenes from carbamoylboranes and their coupling reaction with aldehydes.

Carbamoylboranes were found to react with various aldehydes under heating conditions to give α-hydroxycarboxamides in good yields. A DFT study supports the mechanism, which involves thermally generated (amino)(boryloxy)carbene intermediates. To our knowledge, this is the first report on the generation of (amino)(boryloxy)carbene intermediates from carbamoylboranes and its application to carbon-carbon bond-forming reactions.

Visible-Light-Induced Generation of Fischer-Type Copper Carbene Complexes from Acylsilanes and Its Application to Catalytic [4 + 1] Cycloaddition with Siloxydienes.

A novel methodology for generation of Fischer-type metal-carbene complexes was developed. Photoirradiation to a mixture of an acylsilane and a cationic copper complex cleanly gave a Fischer-type copper-siloxycarbene complex, which was detected by spectroscopic methods. This carbene complex reacted with siloxydienes in a [4 + 1] cycloaddition manner to give cyclopentene derivatives.

Efficient Generation and Synthetic Applications of Alkyl-Substituted Siloxycarbenes: Suppression of Norrish-Type Fragmentations of Alkanoylsilanes by Triplet Energy Transfer.

Acylsilanes have been known to undergo isomerization to siloxycarbenes under photoirradiation and the thus generated carbenes can be utilized for various synthetic reactions. But this carbene formation is not necessarily efficient with some alkanoylsilanes because Norrish-type fragmentations compete, which limit the synthetic utility of alkanoylsilanes as carbene precursors. In this study, generation of siloxycarbenes from alkanoylsilanes by visible-light-induced energy transfer was examined by using an Ir complex, [Ir{dF(CF )ppy} (dtbpy)]PF , and was successfully applied to the C-C coupling reactions with boronic esters or aldehydes.

Lewis Acid-Assisted Photoinduced Intermolecular Coupling between Acylsilanes and Aldehydes: A Formal Cross Benzoin-Type Condensation.

Intermolecular carbon-carbon bond-forming reaction between readily available acylsilanes and aldehydes was achieved under photoirradiation conditions with assistance of a catalytic amount of Lewis acid. Nucleophilic addition of photochemically generated siloxycarbenes to aldehydes followed by 1,4-silyl migration afforded synthetically useful α-siloxyketones. Electrophilic activation of aldehydes by Lewis acid is highly important to realize this reaction efficiently, otherwise the yield of the desired coupling products were significantly decreased.

Total Synthesis of (±)-Englerin A Using An Intermolecular [3+2] Cycloaddition Reaction of Platinum-Containing Carbonyl Ylide.

Total synthesis of (±)-Englerin A has been achieved starting from γ,δ-ynone 5 in 14 steps. The key feature of this synthesis is the highly efficient and stereoselective preparation of 8-oxabicyclo[3.2.

Enantioselective preparation of 8-oxabicyclo[3.2.1]octane derivatives via asymmetric [3+2]-cycloaddition of platinum-containing carbonyl ylides with vinyl ethers.

A catalytic asymmetric synthesis of 8-oxabicyclo[3.2.1]octane derivatives was achieved through the [3+2]-cycloaddition of the platinum-containing carbonyl ylides generated from acyclic gamma,delta-ynones on treatment with 10 mol % of PtCl(2)-Walphos and AgSbF(6).