Allylation of Alcohols and Carboxylic Acids with Allyl Acetate Catalyzed by [Ir(cod)2]+BF4- Complex

Green protocols for Tsuji–Trost allylation: an overview

Since its inception in 1960s, the Tsuji–Trost reaction, an allylic substitution reaction with diverse nucleophiles such as phenols, amines, thiols, and active methylene compounds, has remained as one of the most useful and widely used organic reactions for the construction of C–C and C–heteroatom bonds. Allylic compounds such as allylic acetates, alcohols, halides, and carbonates undergo this transformation which plays an important role in the total synthesis of various natural products. The competence to incorporate synthetically demanding allylic functionalities makes it a beneficial tool for the synthesis of complex molecules. Over the last two decades, major advancements for this unique and facile Tsuji–Trost allylation reaction have been made with special emphasis to develop greener and sustainable protocols. This chapter presents an update on the significant progress focusing on the newly designed catalytic systems with high efficiency, the use of eco-friendly solvents or solvent-free conditions, low or room temperature conditions and waste management, along with future outlook.

Palladium-Catalyzed Decarboxylative O-Allylation of Phenols with γ-Methylidene-δ-valerolactones

A novel Palladium-Catalyzed decarboxylative O-allylation of phenols was developed, in which a γ-methylidene-δ- valerolactone (GMDVs) was found to be an efficient and selective allylation reagent, affording the target allyl phenyl...

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Palladium-Catalyzed Cascade Allylative Dicarbofunctionalization of Aryl Phenol-Tethered Alkynes with Allyl Iodides: Synthesis of Skipped Dienes

A palladium-catalyzed cascade allylative dicarbofunctionalization of aryl phenol-tethered alkynes with allyl iodides is described. A series of polysubstituted spirocyclo-containing skipped dienes with an all-carbon tetrasubstituted alkene unit are synthesized through this convenient process. The cascade reaction proceeds selectively through dearomative C-allylation instead of O-allylation of aryl phenols.

An Electrochemical Method for Carboxylic Ester Synthesis from N-Alkoxyamides

An electrochemical method for the synthesis of carboxylic as well as hindered esters from N-alkoxyamides has been reported. The electrochemical reaction proceeds through constant current electrolysis (CCE) by taking advantage of the dual role of n-Bu₄NI (TBAI) as the redox catalyst as well as the supporting electrolyte. Besides providing mild reaction conditions, the present protocol is free from external oxidants and conducting salts, thereby generating nitrogen as the nonhazardous side product. Additionally, the developed procedure is highly advantageous due to its short reaction time, wide substrate scope, and gram-scale synthesis.

Polymeric β-alanine incarcerated Pd(ii) catalyzed allylic etherification in water: a mild and efficient method for the formation of C(sp3)–O bonds

A new heterogeneous palladium(ii) catalyst has been developed through a convenient and economic way for the synthesis of allyl-aryl ether.

Highly selective palladium-benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions

The Pd–benzothiazol-2-ylidene complex I was found to be a chemoselective catalyst for the Tsuji–Trost allylation of active methylene compounds carried out under neutral conditions and using carbonates as allylating agents. The proposed protocol consists in a simplified procedure adopting an in situ prepared catalyst from Pd₂dba₃ and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed.

Catalytic carbonyl addition through transfer hydrogenation: a departure from preformed organometallic reagents

Classical protocols for carbonyl allylation, propargylation and vinylation typically rely upon the use of preformed allyl metal, allenyl metal and vinyl metal reagents, respectively, mandating stoichiometric generation of metallic byproducts. Through transfer hydrogenative C-C coupling, however, carbonyl addition may be achieved from the aldehyde or alcohol oxidation level in the absence of stoichiometric organometallic reagents or metallic reductants. Here, we review transfer hydrogenative methods for carbonyl addition, which encompass the first catalytic protocols enabling direct C-H functionalization of alcohols.

Hydroxylamines as Oxygen Atom Nucleophiles in Transition-Metal-Catalyzed Allylic Substitution

[reaction: see text] The viability of hydroxylamines as nucleophiles in transition-metal-catalyzed allylic substitutions was examined. We have found that the oxygen atom of hydroxylamines having an N-electron-withdrawing substituent (also known as hydroxamic acids) acts as a reactive nucleophile. The palladium-catalyzed O-allylic substitution of hydroxylamines with allylic carbonate afforded the linear hydroxylamines. The selective formation of the branched hydroxylamines was observed in iridium-catalyzed reaction. Regio- and enantioselective allylic substitution of the unsymmetrical phosphates with hydroxylamines was studied by using the iridium complex of chiral pybox ligand. The aqueous-medium reaction with hydroxylamines proceeded smoothly in the presence of Ba(OH)(2).H(2)O to give the branched products with good enantioselectivities.