Magnesiated unsaturated silylated cyanohydrins as synthetic equivalents of aromatic and heterocyclic grignard reagents bearing a ketone or an aldehyde

[reaction: see text] The preparation of iodo-substituted aryl, heteroaryl, or cycloalkenyl ketones as silylated cyanohydrins allows the smooth performance of an I/Mg-exchange using i-PrMgCl.LiCl. A facile deprotection of the resulting functionalized products obtained by a reaction with electrophiles (acid chlorides, allylic bromide, benzylidene-p-toluenesulfonamide, and 3-iodocyclohexenone) produces polyfunctional ketones in good overall yields. This sequence can be extended to aromatic iodoaldehydes. In these cases, the deprotection of the silylated cyanohydrin functionality is best performed with aqueous CuSO(4) under basic conditions.     

Thermodynamics of hydrogen atom transfer to a high-valent iron imido complex

Thermodynamic investigations relevant to hydrogen atom transfer by the high-valent iron imido complex [LMesFe[triple bond]NAd]OTf have been undertaken. The complex is found to be weakly oxidizing by cyclic voltammetry (E1/2 = -0.98 V vs Cp2Fe+/Cp2Fe in MeCN). A combination of experimental and computational studies has been used to determine the acidity of LMesFe-N(H)Ad+ (pKa = 37 in MeCN), allowing the N-H BDFE (88(5) kcal/mol) to be calculated from a thermodynamic cycle. Consistent with this value, [LMesFe[triple bond]NAd]OTf reacts with 9,10-dihydroanthracene (C-H BDE = 78(1) kcal/mol) to form anthracene.     

Intramolecular C-H bond activation induced by a scandium terminal imido complex

A CpPN-based scandium terminal imido complex was isolated, which could induce the intramolecular C-H bond activation of a phenyl group even at room temperature.     

Organic nitriles from acid chlorides: an isovalent N for (O)CL exchange reaction mediated by a tungsten nitride complex

Nitride NW(N[i-Pr]Ar)3 (1, Ar = 3,5-C6H3Me2) was synthesized in two steps from known NW(O-t-Bu)3 (41% overall yield). Complex 1 is the tungsten congener of NMo(N[i-Pr]Ar)3, a known molecule that has been synthesized using N2 as the nitrido nitrogen source, but which undergoes no reaction with pivaloyl chloride. Compound 1 undergoes metathesis with pivaloyl chloride at 25 degrees C to form the corresponding nitrile in 97% yield. Another substrate examined in this work was the labeled acid chloride 1-Ad13C(O)Cl (Ad = adamantyl). The "(O)Cl" moiety is transferred to tungsten forming an oxo-chloride, (Ar[i-Pr]N)3W(O)Cl (3), as the final tungsten product; both 1 and 3 were characterized structurally by X-ray diffraction. An intermediate observed in the nitrile-forming reaction was characterized spectroscopically to be a tungsten acylimido complex. The latter assignment was substantiated by the synthesis and structural characterization of the compound (Ar[i-Pr]N)3W(NC(O)CF3)(O2CCF3) (2m). In addition, density functional theory calculations performed using ADF lent insight into the thermochemistry of the overall process.     

CAN and iodine-catalyzed reaction of indole or 1-methylindole with α,β-unsaturated ketone or aldehyde

CAN (cerium ammonium nitrate) and iodine can catalyze the reactions of indole or 1-methylindole with α,β-unsaturated ketone or aldehyde in DMSO/H₂O (5:1) or ether solution at room temperature to obtain moderate to high yields of different products.     

The efficient synthesis of carbodiimides using a titanium imido complex

An efficient rt synthesis of carbodiimides or ureas from the combination of a titanium imido complex 2 and a range of 12 aryl and aliphatic isocyanates is described. Control experiments suggest that carbodimide formation is via heterocumulene metathesis through a transient intermediate η²-ureato-N,O metallacycle 8.     

Oxygen reduction to water mediated by a dirhodium hydrido-chloride complex

The two-electron mixed-valence dirhodium complex Rh(2)(0,II)(tfepma)(2)(CN(t)Bu)(2)Cl(2) (tfepma = CH(3)N[P(OCH(2)CF(3))(2)](2)) reacts with HCl to furnish two isomeric dirhodium hydrido-chloride complexes, Rh(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(3)H. In the presence of HCl, the hydride complex effects the reduction of 0.5 equiv of O(2) to 1 equiv of H(2)O, generating Rh(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(4), which can be prepared independently by chlorine oxidation of the Rh(2)(0,II) precursor. The starting Rh(2)(0,II) complex is regenerated photochemically to close an oxygen-to-water reduction photocycle.     

Isocyanate and carbodiimide synthesis by nitrene-group-transfer from a nickel(II) imido complex

The imido complex (dtbpe)Ni(N(2,6-(CHMe2)2C6H3)) reacts with CO and CNCH2Ph with addition at the Ni-N bond to give (dtbpe)Ni(C,N:eta 2-C(O)N(2,6-(CHMe2)2C6H3)) and (dtbpe)Ni(C,N:eta 2-C(NCH2Ph)N(2,6-(CHMe2)2C6H3)); both complexes react further with CO to liberate the isocyanate and carbodiimide ligands with formation of (dtbpe)Ni(CO)2.     

Efficient aldehyde olefination reactions catalyzed by an iron porphyrin complex in an ionic liquid

The commercially available complex Fe(TPP)Cl is an active and highly (E)-selective catalyst for the olefination of a variety of aldehydes in the presence of PPh₃ and diazoacetate in the ionic liquid (bmim)(PF₆). Dependent on the reactivity of the applied aldehyde, the reaction can be carried out at a reaction temperature of 50-80 °C. After 0.5-24 h quantitative olefin yields are reached with a broad variety of different aldehydes. Due to the application of an ionic liquid as reaction medium the products can be easily removed from the catalyst by a simple extraction and the catalyst is conveniently reusable without significant activity loss. Spectroscopic investigations indicate that the reaction mechanism includes the quantitative formation of a phosphorus ylide, which then reacts further in a Wittig reaction under formation of an olefin.     

Scandium terminal imido complex induced C-H bond selenation and formation of an Sc-Se bond

The reaction between scandium terminal imido complexes and elemental selenium showed an unprecedented C-H bond selenation and the formation of an Sc-Se bond.     

Unusual thermal C-h bond activation by a tungsten allene complex

Gentle thermolysis of the 18e alkyl-allyl complex, CpW(NO)(CH(2)CMe(3))(eta(3)-3,3-Me(2)C(3)H(3)) (1), generates a reactive 16e allene intermediate, CpW(NO)(eta(2)-CH(2)=C=CMe(2)) (A), with the concomitant evolution of neopentane via hydrogen abstraction from the dimethylallyl ligand. A has been structurally characterized as its PMe(3) adduct and is capable of effecting single and multiple C-H bond activations of hydrocarbon solvents. For example, the thermal reaction of 1 with cyclohexane leads to the formation of the 18e cyclohexenyl hydrido complex, CpW(NO)(eta(3)-C(6)H(9))(H) (5), as a result of three successive C-H activations of the alkane solvent.     

Convenient method for the transformation of epoxide to aldehyde and acetonide mediated by Cr-PLM

Chromium-pillared montmorillonite (Cr-PLM) could be synthesized and efficiently utilized for styrene oxide transformations. The target aldehyde product could be quantitatively achieved from the isomerization of styrene oxide by using 10?wt% of Cr-PLM under reflux temperature for 15?min. The acetonide product could be achieved in excellent yield from the reaction of styrene oxide and acetone by using 10?wt% of Cr-PLM under room temperature for 20?min. The catalyst could be recovered and reused at least five times without loss of activity.     

Synthesis and characterization of a neutral rhenium(V) complex containing a tridentate chelate with an imido donor atom

The six-coordinate complex cis-[Re(mps)Cl₂(PPh₃)] (1) (H₃mps?=?N-(2-amino-3-methylphenyl)-salicylideneimine) was prepared the reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of H₃mps in benzene. The compound was characterized by spectroscopy and single-crystal X-ray crystallography. Mps coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the phenolate oxygen atoms. The imide and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.