Hypervalent Iodine(III)-Catalysed Enantioselective α-Acetoxylation of Ketones.

An enantioselective catalytic synthesis of α-acetoxylated ketones through I(I)/I(III) catalysis using a resorcinol/lactamide-based chiral iodoarene is reported. Catalyst turnover by in situ generation of the active iodine(III) derivative is achieved by oxidation with mCPBA in the presence of acetic acid. The prior transformation of ketones to easily accessible acetyl enol ethers is beneficial and yields up to 97 % with enantioselectivities up to 88 % ee are obtained using only low catalyst loadings of only 5 mol % under mild reaction conditions.

Structurally Defined α-Tetralol-Based Chiral Hypervalent Iodine Reagents.

A novel class of chiral hypervalent iodine reagents containing an α-tetralol scaffold is introduced. Iodine triacetate is employed in a key step as a highly selective and efficient iodinating reagent for a short and convenient synthesis of iodine(III) derivatives. Solid-state X-ray analyses offer valuable structural information, while reactivities and stereoselectivities are investigated in three model reactions.

Alternative Strategies with Iodine: Fast Access to Previously Inaccessible Iodine(III) Compounds.

Non-iodinated arenes can be easily and selectively converted into (diacetoxyiodo)arenes in a single step under mild conditions by using iodine triacetates as reagents. The oxidative step is decoupled from the synthesis of hypervalent iodine(III) reagents, which can now be prepared conveniently in a one-pot synthesis for subsequent reactions without prior purification. The chemistry of iodine triacetates was also expanded to heteroatom ligand exchanges to form novel inorganic hypervalent iodine compounds.

Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane.

A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.

Ethyl Lithiodiazoacetate: Extremely Unstable Intermediate Handled Efficiently in Flow.

Ethyl diazoacetate (EDA) is one of the most prominent diazo reagents. It is frequently used in metal-carbene-type reactions. However, EDA can also be used as a nucleophile under base catalysis. Whilst the addition of EDA to aldehydes can be performed using organic bases, the addition of EDA to other carbonyl electrophiles requires the use of organometallics such as lithium diisopropylamide (LDA). The generated ethyl lithiodiazoacetate is highly reactive and decomposes rapidly, even at low temperatures. Herein, we report a continuous flow protocol that overcomes the problems associated with the instantaneous decomposition of ethyl lithiodiazoacetate. The addition of ethyl lithiodiazoacetate to ketones provides direct access to tertiary diazoalcohols in good yields.