N-Tosyl Hydrazone Precursor for Diazo Compounds as Intermediates in the Synthesis of Aluminum Complexes

Silver-Promoted Rapid Synthesis of 3-Arylindan-1-ones: Microwave-Assisted Reductive Coupling of N-Tosylhydrazone and Boronic Acids

An efficient and straightforward one-pot tandem synthesis of 3-arylindan-1-ones was consummated through silver nitrate-promoted C-C coupling of simple indane-1,3-dione with arylboronic acid via 1,3-indanedione monotosylhydrazone under microwave conditions. The resulting series of 3-arylindan-1-ones exhibited impressive yields, surpassing those achievable with traditional methods and requiring a shorter time frame. This innovative approach significantly accelerated the synthesis of biologically active compounds such as (+)-indatraline (Lu 19-005) and several other industrially relevant substances.

Aluminium-Catalyzed Selective Hydroboration of Esters and Epoxides to Alcohols: C-O Bond Activation

In this work, the molecular aluminium dihydride complex bearing an N, N'-chelated conjugated bis-guanidinate (CBG) ligand is used as a catalyst for reducing a wide range of aryl and alkyl esters with good tolerance of alkene (C=C), alkyne (C≡C), halides (Cl, Br, I and F), nitrile (C≡N), and nitro (NO₂ ) functionalities. Further, we investigated the catalytic application of aluminium dihydride in the C-O bond cleavage of alkyl and aryl epoxides into corresponding branched Markovnikov ring-opening products. In addition, the chemoselective intermolecular reduction of esters over other reducible functional groups, such as amides and alkenes, has been established. Intermediates are isolated and characterized by NMR and HRMS studies, which confirm the probable catalytic cycles for the hydroboration of esters and epoxides.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Oxidative Addition of Hydridic, Protic, and Nonpolar E-H Bonds (E = Si, P, N, or O) to an Aluminyl Anion

The aluminyl anion K[Al(NON^Dipp)] {NON^Dipp = [O(SiMe₂NDipp)₂]^2-; Dipp = 2,6-iPr₂C₆H₃} engages in oxidative additions with the E-H (E = Si, P, N, or O) bonds of phenylsilane (PhSiH₃), mesityl phosphane (MesPH₂; Mes = 2,4,6-Me₃C₆H₂), 2,6-di-iso-propylaniline (DippNH₂), and 2,6-di-tert-butyl-4-methylphenol (ArOH). The resulting (hydrido)aluminate salts are formed regardless of the E-H bond polarity. All of the products were characterized by nuclear magnetic resonance and infrared spectroscopic techniques and single-crystal X-ray diffraction. This study highlights the versatility of aluminyl anions to activate hydridic, acidic, and (essentially) nonpolar E-H bonds.

Effect and Mechanism of Aluminum(III) for Guaiacol-Glyoxylic Acid Condensation Reaction in Vanillin Production

3-methoxy-4-hydroxymandelic acid (VMA) was the critical intermediate for the synthesis of vanillin by the glyoxylic acid method. Meanwhile, a valuable byproduct (2-hydroxy-3-methoxy-mandelic acid, o-VMA) was obtained during the reaction. Al3+ was found to be a helpful catalyst in increasing the selectivity for VMA and o-VMA. In the presence of Al3+, the selectivity for VMA and o-VMA increased from 83 to 88% and from 3 to 8%, respectively, while that of the helpless byproduct 2-hydroxy-3-methoxy-1,5-mandelic acid (di-VMA) decreased from 14% to less than 4%. The kinetics based on the kinetic equation of the condensation reaction was studied by the initial concentration method. The results indicated that the involvement of Al3+ could reduce the activation energy of the reaction on the basis of the Arrhenius equation. Combined with thermogravimetric analysis, in situ Fourier transform-infrared spectroscopy, and 1H NMR research, Al3+ was found to interact with guaiacol through Al-O and Al···H, which further improved the selectivity of the VMA and o-VMA and reduced the selectivity of di-VMA by adding the electronegativity of the ortho- and para-positions of hydroxyl groups of guaiacol.

Mono- and Bimetallic Aluminum Alkyl, Alkoxide, Halide and Hydride Complexes of a Bulky Conjugated Bis-Guanidinate(CBG) Ligand and Aluminum Alkyls as Precatalysts for Carbonyl Hydroboration

Tetra-aryl-substituted symmetrical conjugated bis-guanidine (CBG) ligands such as L^1-3 (3H) [L(3H) = {(ArHN)(ArHN)C═N-C═NAr(NHAr)}; Ar = 2,6-Me₂-C₆H₃ (L¹(3H)), 2,6-Et₂-C₆H₃ (L²(3H)), and 2,6-ⁱPr₂-C₆H₃ (L³(3H))] have been employed to synthesize a series of four- and six-membered aluminum heterocycles (1-8) for the first time. Generally, aluminum complexes bearing N,N'- chelated guanidinate and β-diketiminate/dipyrromethene ligand systems form four- and six-membered heterocycles, respectively. However, the conjugated bis-guanidine ligand has the capability of forming both four- and six-membered heterocycles possessing multimetal centers within the same molecule; this is due to the presence of three acidic protons, which can be easily deprotonated (at least two protons) upon treatment with metal reagents. Both mono- and dinuclear aluminum alkyls and mononuclear aluminum alkoxide, halide, and hydride complexes have been structurally characterized. Further, we have demonstrated the potential of mononuclear, six-membered CBG aluminum dialkyls in catalytic hydroboration of a broad range of aldehydes and ketones with pinacolborane (HBpin).

Organoaluminum Compounds as Catalysts for Monohydroboration of Carbodiimides

The effective catalytic activity of organoaluminum compounds for the monohydroboration of carbodiimides has been demonstrated. Two aluminum complexes, 2 and 3, were synthesized and characterized. The efficient catalytic performances of four aluminum hydride complexes L1 AlH2 (L1 =HC(CMeNAr)2 , Ar=2,6-Et2 C6 H3 ; 1), L2 AlH2 (NMe3 ) (L2 =o-C6 H4 F(CH=N-Ar), Ar=2,6-Et2 C6 H3 ; 2), L3 AlH (L3 =2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine; 3), and L4 AlH(NMe3 ) (L4 =o-C6 H4 (N-Dipp)(CH=N-Dipp), Dipp=2,6-iPr2 C6 H3 ; 4), and an aluminum alkyl complex L1 AlMe2 (5) were used for the monohydroboration of carbodiimides investigated under solvent-free and mild conditions. Compounds 1-3 and 5 can produce monohydroborated N-borylformamidine, whereas 4 can afford the C-borylformamidine product. A suggested mechanism of this reaction was explored, and the aluminum formamidinate compound 6 was characterized by single-crystal X-ray, also a stoichiometric reaction was investigated.

Synthesis and Characterization of Pheox- and Phebox-Aluminum Complexes: Application as Tunable Lewis Acid Catalysts in Organic Reactions

Pheox- and Phebox-aluminum complexes were synthesized and subsequently characterized by spectroscopic analysis. These complexes acted as Lewis acid catalysts, and their catalytic activities were controlled by using the Pheox, Phebox, and heteroatom ligands. The Pheox-aluminum complex exhibited an opposite substrate selectivity to AlCl₃ in a competitive hetero-Diels-Alder reaction between electron-rich and electron-deficient aldehydes.

Reversible borohydride formation from aluminium hydrides and {H(9-BBN)}2: structural, thermodynamic and reactivity studies

A series of novel β-diketiminate stabilised aluminium borohydrides of the type (Nacnac)Al(R){H₂(9-BBN)} has been synthesised offering variation in both the auxiliary R substituent and in the Nacnac backbone itself. A number of these complexes show unusual dissociation of the borane from the aluminium hydride in solution under ambient conditions. The lability of the borane is shown (by variable temperature NMR analyses) to be influenced by the electronic character of both the aluminium-bound R substituent and the Nacnac ligand itself, such that electron-withdrawing substituents lead to greater dissociation of the borane. Comparison of these complexes with related systems featuring the tetrahydroborate [BH₄]^- ligand illustrates the impact of the boron-bound substituents on the ability of the borane fragment to dissociate from the aluminium hydride. This dissociative behaviour is shown to be highly influential on the ability of the borohydride complexes to reduce carbon dioxide in a stoichiometric manner.