N-Iodophthalimide as a halogen bond donor, a comparison with N-iodosuccinimide and N-iodosaccharin

The halogen bond (HaB) donor ability of N-iodophthalimide (NIPht) is evaluated in its crystal structure, in its neutral adducts with different pyridines, and in its anionic symmetric complex with the phthalimidate anion.

Lewis Base-assisted Arylation of Unsaturated Carbonyls

The combination of Lewis bases with α,β-unsaturated carbonyls allows the in-situ generation of enolates without the need for strong Brønsted bases. Recently developed synthetic methods employ this approach for arylation followed by elimination of the Lewis base, regenerating the alkene. This strategy has been deployed for formal α- or β-C-H arylation in different contexts, namely (a) transition metal catalysis, (b) rearrangement reactions utilizing hypervalent main group elements and (c) organocatalysis. This concept article provides an overview of the developed strategies, highlighting and contextualizing their features.

α-Iodo-α,β-Unsaturated Ketones as Vicinal Dielectrophiles: Their Reactions with Dinucleophiles Provide New Annulation Protocols for the Formation of Carbo- and Heterocyclic Ring Systems

α-Iodo-α,β-unsaturated ketones such as compound 1 serve as vicinal dielectrophiles and react with a range of dinucleophiles including pentane-2,4-dione and 1,3-indandione to produce [3 + 2]- and [2 + 1]-adducts such as 5 and 38, respectively. [4 + 2]- and [5 + 2]-cycloadducts have been obtained from compound 1 by related means. Preliminary studies reveal that α-iodinated α,β-unsaturated esters can also participate in at least some of these same processes.

Highly regioselective α-alkylation of α,β,γ,δ-unsaturated aldehydes

The first α-alkylation of α,β,γ,δ-unsaturated aldehydes is achieved under mild reaction conditions. Several α,β,γ,δ-unsaturated aldehydes and diarylcarbinols are successfully tested for the synthesis of MBH-type α-alkylated products with an excellent regioselectivity. Simple pyrrolidine is efficiently used as a catalyst to achieve a perfect E/Z selectivity of the α-alkylated products.

Recent advancements on the use of 2-methyltetrahydrofuran in organometallic chemistry

ABSTRACT

Since the introduction of 2-methyltetrahydrofuran as an useful alternative to the classical tetrahydrofuran, there has been a continuous interest in the synthetic community operating at academic and industrial towards it. In particular, the much higher stability that basic organometallic reagents display in 2-methyltetrahydrofuran makes it suitable for processes involving such sensitive species including asymmetric transformations. The easy formation of an azeotropic mixture with water, the substantial immiscibility with water, and the fact it derives from natural sources (corncobs or bagasse), allow to consider it in agreement with the Anastas' Geen Chemistry principles. In this minireview, selected examples of its employment in organometallic transformations ranging from carbanions to radical and transition metal-catalyzed processes are provided.

GRAPHICAL ABSTRACT

Catalyst-Free Halogenation of α-Diazocarbonyl Compounds with N-Halosuccinimides: Synthesis of 3-Halooxindoles or Vinyl Halides

A novel catalyst-free halogenative cyclization of N-aryl diazoamides with N-halosuccinimides (NXS) is reported for the synthesis of 3-halooxindoles through a carbene-free mechanism. N-Aryl diazoamides reacted with NXS under mild and catalyst-free conditions to afford the corresponding 3-halooxindoles in good yields. This transformation is proposed to proceed through diazonium ion formation followed by intramolecular Friedel-Crafts alkylation.

Synthesis of 1,3-dibromo-2-aryl-1H-indenes via NBS mediated unusual bromination of 2-alkynylbenzaldoximes

An interesting side-pathway leading to 1,3-dibromo-2-aryl-1H-indenes as opposed to isoquinoline N-oxides via NBS mediated bromination of 2-alkynylbenzaldoximes.

Catalytic MBH reaction of β-substituted nitroalkenes with azodicarboxylates

An unprecedented N-heterocyclic carbene (NHC) catalyzed Morita-Baylis-Hillman (MBH) reaction of β-substituted nitroalkenes and azodicarboxylates has been developed. Both β-aryl and β-alkyl nitroalkenes worked well for the reaction using 5 mol% of NHC catalyst, giving the desired α-hydrazino-α,β-unsaturated nitroalkenes in good to excellent yields.

Metal free stereoselective synthesis of functionalized enamides

An efficient and expeditious DABCO-mediated synthesis of functionalized enamides from alkenes is delineated. The reaction proceeds through an unprecedented cascade involving an Aza-Michael addition/α-bromination/elimination and a Morita-Baylis-Hillman type reaction to generate functionalized enamides in a regio- & stereoselective fashion.