Trimethylsilyl Cyanide Addition to Carbonyl Compounds Under Neutral Condition Catalyzed by Iodine

Reaction of trimethylsilyl cyanide with aliphatic or aromatic aldehydes and ketones in the presence of a catalytic amount of elemental iodine produced the corresponding cyanohydrin trimethylsilyl ethers in very short time and high yields.     

Yttrium‐Catalyzed Intramolecular Hydroalkoxylation/Claisen Rearrangement Sequence: Efficient Synthesis of Medium‐Sized Lactams

An efficient yttrium‐catalyzed intramolecular hydroalkoxylation/Claisen rearrangement sequence has been achieved, thus enabling facile access to a diverse array of valuable medium‐sized lactams. Furthermore, a mechanistic rationale for this novel cascade reaction is well supported by a variety of control experiments.     

Synthesis and Crystal Structure of a Rare Tetra‐Yttrium‐Supported Krebs‐Type Tungstoantimonate

A rare tetra‐yttrium‐supported Krebs‐type tungstoantimonate was prepared in an acidic solution at pH 2.2 and characterized by elemental analysis and IR spectroscopy. Single‐crystal X‐ray analysis was carried out on Na₂[{Y(H₂O)₇}₄Sb₂W₂₂O₇₆]·14H₂O ( 1 ), which comprises a Krebs‐type [Sb₂W₂₂O₇₆]^14– unit supported by four yttrium ions.     

Highly Syndiotactic or Isotactic Polyhydroxyalkanoates by Ligand‐Controlled Yttrium‐Catalyzed Stereoselective Ring‐Opening Polymerization of Functional Racemic β‐Lactones

Reported herein is the first stereoselective controlled ROP of a specific family of racemic functional β‐lactones, namely 4‐alkoxymethylene‐β‐propiolactones (BPL^ORs). This process is catalyzed by an yttrium complex stabilized by a nonchiral tetradentate amino alkoxy bisphenolate ligand {ONOO^R′2}²⁻, which features both a good activity and a high degree of control over the molar masses of the resulting functional poly(3‐hydroxyalkanoate)s. A simple modification of the R′ substituents in ortho and para position on the ligand platform allows for a complete reversal from virtually pure syndioselectivity (P_s up to 0.91 with R′=cumyl) to very high isoselectivity (P_i up to 0.93 with R′=Cl), as supported by DFT insights. This is the first example of a highly isoselective ROP of a racemic chiral β‐lactone.     

Heterocyclic Carbene‐Catalyzed Hydride Transfer in the Hydroboration of Carbonyl Compounds

N‐Heterocyclic carbene (NHC) enabled the highly efficient catalytic hydroboration of a wide range of ketones and aldehydes under mild conditions, and a new mechanism of catalytic hydroboration reaction which involves direct hydride transfer is proposed.     

Quantum Chemical Investigation of the Initial Steps of the Yttrium‐Mediated Polymerization of Ethene and Propene

The mechanistic details of the initial steps of the polymerization brought about by a dicyclopentadienyl yttriumhydrid catalyst have been computationally investigated using approximate density functional theory. In accord with the experimental information, the overall reaction sequence Cp₂YH + C₂H₄ → Cp₂Y–C₂H₅ and Cp₂YH + C₃H₆ → Cp₂Y–C₃H₇ is computed to be exothermic by ca. 22.2 and 20.8 kcal mol^–1, respectively. The reaction mechanism predicted by our calculations is in harmony with the available experimental information but provides additional information into the various elementary steps of this reaction, which could not be obtained by experimental means.     

Gold‐Catalyzed Reactions of 1,5‐ and 1,6‐Enynes with Carbonyl Compounds: Cycloaddition vs. Metathesis

Gold and rings : The gold(I)‐catalyzed addition of aldehydes to 1,6‐enynes gives 1,3‐dienes, by a cycloaddition/fragmentation process. 1,5‐Enynes react with aldehydes and ketones by the 5‐endo‐dig pathway to give the corresponding cycloadducts.

     

Copper‐Catalyzed Cyanations of Aromatic Bromides with Benzoyl Cyanide

Aromatic nitriles were synthesized through copper‐catalyzed cyanations of aromatic bromides using benzoyl cyanide as the cyanide source. A series of functional groups were tolerated under the reaction conditions to provide the products in good yields. Moreover, this protocol avoids using of highly toxic alkali cyanides and expensive palladium catalysts.     

Highly Selective Hydroboration of Alkenes,Ketones and Aldehydes Catalyzed by a Well‐Defined Manganese Complex

Well‐defined manganese complexes based on inexpensive, readily available ligands, 2,2′:6′,2′′‐terpyridine and its derivatives have been prepared and employed for the selective hydroboration of alkenes, ketones and aldehydes. Highly Markovnikov regioselective hydroboration of styrenes as well as excellent chemoselective hydroboration of ketones over alkenes were achieved, for the first time, by an earth‐abundant manganese catalyst.     

Iridium‐Catalyzed β‐Alkynylation of Aliphatic Oximes as Masked Carbonyl Compounds and Alcohols

An Ir‐catalyzed C(sp³)?H alkynylation of aliphatic ketones, aldehydes, and alcohols was achieved by using the corresponding oxime derivatives and a Ir^III catalyst. This general reaction is selective towards primary C(sp³)?H bonds and can be used for the late‐stage C?H alkynylation of complex molecules.