Investigation of sp2–sp Coupling for Electron‐Enriched Aryl Dihalides under Oxygen‐Free Sonogashira Coupling Reaction Conditions Using a Two‐Chamber Reaction System

Triethylamine hydroiodide crystals were formed during Sonogashira reactions; after complete reaction the solution retains a characteristic light color (see picture). Very sluggish Sonogashira reactions of electron‐enriched aryl diiodides have been carried out in high yield in an oxygen‐free, two‐chamber reaction system. The formation of triethylamine hydroiodide crystals was monitored to determine the completion of reaction.

     

“Design” of Boron‐Based Compounds as Pro‐Nucleophiles and Co‐Catalysts for Indium(I)‐Catalyzed Allyl Transfer to Various Csp3‐Type Electrophiles

We have recently uncovered a general indium(I)‐catalyzed method for allylations and propargylation of acetals and ketals with a water‐ and air‐stable allyl boronate. By using a more reactive allyl borane, we have successfully extended this methodology to the more challenging C C coupling with ethers. Herein, we report an improved methodology for the indium(I)‐catalyzed allylation of acetals and ethers, through combination of the allyl boronate with a commercially available “hard” Lewis acid, B‐methoxy‐9‐BBN (BBN=borabicyclo[3.3.1]nonane), as an effective co‐catalyst. Significantly, our work highlights for the first time the correlation between the Lewis acidity of “electrophilic” boron‐based compounds and their “nucleophilic” reactivity in Csp³–Csp³ couplings, catalyzed by a “soft” low‐oxidation main group metal. In addition, we also report several applications of these methodologies to the selective synthesis of various carbohydrate derivatives.     

Macrocyclization by Nickel‐Catalyzed,Ester‐Promoted,Epoxide–Alkyne Reductive Coupling: Total Synthesis of (−)‐Gloeosporone

Ringing the changes : The total synthesis of the title compound centers around a novel strategy that employs a nickel(0)–phosphine complex and triethyl borane in an efficient closure of a 14‐membered ring through C? C bond formation (see scheme; cod=cyclooctadiene). The synthesis was accomplished in 10 steps and in approximately 9 % overall yield.

     

Aerobic and Electrochemical Oxidative Cross‐Dehydrogenative‐Coupling (CDC) Reaction in an Imidazolium‐Based Ionic Liquid

The ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [BMIm][BF₄] has demonstrated high efficiency when applied as a solvent in the oxidative nitro‐Mannich carbon? carbon bond formation. The copper‐catalyzed cross‐dehydrogenative coupling (CDC) between N‐phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF₄] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and β‐nitroamine product was investigated employing [BMIm][BF₄] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.     

Post‐Modification of meso–meso‐Linked Porphyrin Arrays by Iridium and Rhodium Catalyses for Tuning of Energy Gap

Skillfully attached! meso–meso‐Linked diporphyrins can be efficiently and selectively functionalized with multiple unsaturated carboxylic acid groups through iridium and rhodium catalyses. This post‐modification strategy allows fine‐tuning of energy levels of each porphyrin unit.

     

Palladium‐Catalyzed Carbon–Carbon Bond Formation and Cleavage of Organo(hydro)fullerenes

Palladium can tailor fullerenes : Palladium catalysts enable a number of C? H bond transformations of organo(hydro)fullerene. In addition to anticipated coupling reactions (C? H bond allylation and arylation), an unexpected new C? H bond dimerization reaction and C? C bond‐cleavage reaction were also uncovered.

     

General One‐Pot Reductive gem‐Bis‐Alkylation of Tertiary Lactams/Amides: Rapid Construction of 1‐Azaspirocycles and Formal Total Synthesis of (±)‐Cephalotaxine

Amides are a class of highly stable and readily available compounds. The amide functional group constitutes a class of powerful directing/activating and protecting group for C? C bond formation. Tertiary tert‐alkylamine, including 1‐azaspirocycle is a key structural feature found in many bioactive natural products and pharmaceuticals. The transformation of amides into tert‐alkylamines generally requires several steps. In this paper, we report the full details of the first general method for the direct transformation of tertiary lactams/amides into tert‐alkylamines. The method is based on in situ activation of amide with triflic anhydride/2,6‐di‐tert‐butyl‐4‐methylpyridine (DTBMP), followed by successive addition of two organometallic reagents of the same or different kinds to form two C? C bonds. Both alkyl and functionalized organometallic reagents and enolates can be used as the nucleophiles. The method displayed excellent 1,2‐ and good 1,3‐asymmetric induction. Construction of 1‐azaspirocycles from lactams required only two steps or even one‐step by direct spiroannelation of lactams. The power of the method was demonstrated by a concise formal total synthesis of racemic cephalotaxine.     

Transition‐Metal‐Catalyzed Laboratory‐Scale Carbon–Carbon Bond‐Forming Reactions of Ethylene

Ethylene, the simplest alkene, is the most abundantly synthesized organic molecule by volume. It is readily incorporated into transition‐metal‐catalyzed carbon–carbon bond‐forming reactions through migratory insertions into alkylmetal intermediates. Because of its D_2h symmetry, only one insertion outcome is possible. This limits byproduct formation and greatly simplifies analysis. As described within this Minireview, many carbon–carbon bond‐forming reactions incorporate a molecule (or more) of ethylene at ambient pressure and temperature. In many cases, a useful substituted alkene is incorporated into the product.