HFIP-mediated 2-aza-Cope rearrangement: metal-free synthesis of α-substituted homoallylamines at ambient temperature.

An efficient metal-free strategy for the synthesis of α-substituted homoallylamine derivatives has been developed via a 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)-promoted 2-aza-Cope rearrangement of aldimines, generated in situ by condensation of aldehydes with easily accessible 1,1-diphenylhomoallylamines. This reaction provides rapid access to α-substituted homoallylamines with excellent functional group tolerance and yields. The reaction takes place at room temperature and no chromatographic purification is required for product isolation. The synthetic utility of the current method is further demonstrated by the transformation of the obtained benzophenone ketimines into N-unprotected homoallylamines, an α-amino alcohol and an α-amino amide.

Lewis acidic FeCl3 promoted 2-aza-Cope rearrangement to afford α-substituted homoallylamines in dimethyl carbonate.

The iron(iii)-catalyzed efficient strategy for the synthesis of α-substituted homoallylamines was accomplished via a cationic 2-aza-Cope rearrangement of aldimines, generated in situ by condensation of commercially available aldehydes and easily synthesizable 1,1-diphenylhomoallylamines. This reaction features a broad substrate scope with high yields and is conducted in an eco-friendly solvent, i.e. dimethyl carbonate.

The Use of Calcium Carbide as Acetylene Source in a Three-Component Coupling with ω-Chlorinated Ketones and Primary Amines.

Calcium carbide was used in a CuI -catalysed three-component coupling with ω-chlorinated ketones and primary amines to generate terminal 2-alkynyl-N-heterocycles. The formation of an imine and the subsequent intramolecular substitution results in an active electrophilic iminium species, which can be alkynylated by in situ formed copper acetylide. A number of aliphatic primary (functionalised) amines and aliphatic or aromatic alkynes together with different alkyl- or aryl-substituted γ- or δ-chloroketones could be used. Simple acid-base workup instead of column chromatography can be applied to obtain the resulting 2-alkynylpyrrolidines and 2-alkynylpiperidines.

Substituent-Directed Regioselective Azidation: Copper-Catalyzed C-H Azidation and Iodine-Catalyzed Dearomatizative Azidation of Indole.

Azidation of indoles using iodine and copper bromide as catalysts under ambient reaction conditions is presented. The regioselectivity is directed by the substituent at the C3-position of indole. A radical stabilizing group such as an ester or ketone moiety at the C3-position of indole leads to azidation at the C2-position, whereas a less radical stabilizing group such as an alkyl or amide group at the C3-position of indole furnishes the 3-azidooxindole product. This protocol is mild and efficient to obtain several 2-azidoindole derivatives and 3-azidooxindole derivatives in moderate to good yields. The reaction conditions hold well for gram-scale synthesis.

Pd-Boron-Catalyzed One Carbon Isomerization of Olefins: Water Assisted Process at Room Temperature.

A palladium-boronate/borane-system -catalyzed isomerization of olefins has been uncovered. An efficient catalytic combination of [Pd(OAc)2]3-boronate-PCy3-enabled olefin isomerization at 80 °C has been investigated. Addition of water to the reaction showed a remarkable improvement and the isomerization occurred at ambient temperature. These catalytic systems function efficiently for the isomerization of functionalized as well as unfunctionalized olefins. The catalytic conditions demonstrate the involvement of both nonhydride and metal-hydride medium and can be switchable with water as an additive.

Generation of Hydrogen from Water: A Pd-Catalyzed Reduction of Water Using Diboron Reagent at Ambient Conditions.

Production of hydrogen from renewable sources, particularly from water, is an intensive area of research, which has far-reaching relevance in hydrogen economy. A homogeneous catalytic method is presented for producing clean hydrogen gas from water, in a reaction of water with a diboron compound as the reductant, under ambient reaction conditions. The Pd-catalytic system is stable in water and displays excellent recyclability. Hydroxy analogues such as alcohols are compatible with the Pd/B2Pin2 system and generate hydrogen gas efficiently. The B2Pin2-H2O system, in the presence of palladium, is an excellent catalytic system for selective hydrogenation of olefins.

Synthesis of α-sulfenyl monoketones via a metal-free oxidative cross dehydrogenative coupling (CDC) reaction.

α-Sulfenyl ketones are potential precursors which find a variety of applications in organic synthesis. Their typical synthesis requires pre-functionalized starting materials and two to three step synthetic sequences. In addition, the selective pre-functionalization of unsymmetrical ketones is a challenge, which limits the synthesis of the desired sulfenylated ketones. To overcome these disadvantages, a metal-free, convenient one-step strategy for synthesizing α-sulfenyl ketones at ambient temperature via a cross-dehydrogenative coupling (CDC) strategy has been developed with a broad substrate scope. Therefore, this CDC strategy for C-S bond formation is attractive and may find wide applications in organic synthesis.

Sulfenylation of ß-Diketones Using C-H Functionalization Strategy.

Sulfenylation of ß-diketones is challenging as ß-diketones undergo deacylation after sulfenylation in the reaction medium. The sulfenylation of ß-diketones without deacylation under metal-free conditions at ambient temperature via a cross dehydrogenative coupling (CDC) strategy is reported. The resultant products can be further manipulated to form α,α-disubstituted ß-diketones and pyrazoles.