A series of (NHC)Au I Cl (1, NHC ) N, N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr); 2, NHC ) N, N′-bis(2,4,6-trimethylphenyl) N′-bis(2,4,6-trimethylphenyl)complexes were reacted with LiBr to generate [(IPr)AuBr] (8), [(IMes)AuBr] (9), [(SIPr)AuBr] (10), [(SIMes)AuBr] (11), [(ICy)AuBr] (12), [(IAd)-AuBr] (13), and [(I t Bu)AuBr] (14). These (NHC)Au I Br complexes undergo oxidative addition of elemental bromine, leading to the new Au(III) complexes [(IPr)AuBr 3 ] (15), [(IMes)AuBr 3 ] (16), [(SIPr)AuBr 3 ] (17), [(SIMes)AuBr 3 ] (18), [(ICy)AuBr 3 ] (19), [(IAd)AuBr 3 ] (20), and [(I t Bu)AuBr 3 ] ( 21). Complete characterization by NMR spectroscopy and single-crystal X-ray diffraction were performed in order to discern structural differences between organogold(I/III) congeners. A preliminary study examining the activity of (NHC)Au III species on the addition of water to alkynes is also presented.

Imidazol-2-ylidenes, a family of N-heterocyclic carbenes (NHC), are efficient catalysts in the transesterification involving numerous esters and alcohols. Low catalyst loadings of aryl- or alkyl-substituted NHC catalysts mediate the acylation of alcohols with enol acetates in short reaction times at room temperature. Commercially available and more difficult to cleave methyl esters react with primary alcohols in the presence of alkyl-substituted NHC to efficiently form the corresponding esters. While primary alcohols are selectively acylated over secondary alcohols with use of enol esters as acylating agents, methyl and ethyl esters can be employed as protective agents for secondary alcohols in the presence of the more active alkyl-substituted NHC catalysts. The NHC-catalyzed transesterification protocol was simplified by generating the imidazol-2-ylidene catalysts in situ.

| Chem. Rev. 2012, 112, 4642−4686 4.4.3. Enantioselective Synthesis of Various Heterocyclic Compounds via ROM-RCM Domino Metathesis of Ring-Opened Vince Lactam Derivatives 4669 4.5. Use of Vince Lactam as a Standard in Chemical Analysis of Compounds and Optical Activity of Stereoisomers 4669 5. Conclusions 4669 Author Information 4669 Corresponding Author 4669 Notes 4669 Biographies 4670 Acknowledgments 4670 Abbreviations 4670 References 4671V). The well-known preference of the hydrolase enzymes to attack a substrate from si face rather than re face was studied in the system via molecular modeling of the two tetrahedral intermediates. These studies revealed that the complexes modeled on re face for both the isomers of the racemate were highly unfavorable. Furthermore, the unpropitious steric Scheme 12. Biocatalytic Resolution of Vince Lactam Followed by Various Chemical Transformations to Obtain the Desired Stereoisomers of Synthetic Intermediates Scheme 13. Proposed Mechanistic Pathway for the Biocatalytic Hydrolysis of Vince Lactam Chemical Reviews Review dx.