Synthesis and Reactivity of New Rhenium(I) Complexes Containing Iminophosphorane-Phosphine Ligands: Application to the Catalytic Isomerization of Propargylic Alcohols in Ionic Liquids

Abstract

[ReBr(CO)5] reacts with the iminophosphorane-phosphine ligands Ph2PCH2P(═NR)Ph2 (R = P(═O)(OEt)2 (1a), P(═O)(OPh)2 (1b), P(═S)(OEt)2 (1c), P(═S)(OPh)2 (1d), 4-C6F4CHO (1e), 4-C6F4CN (1f), 4-C5F4N (1g)) affording the neutral complexes [ReBr(κ(2)-P,X-Ph2PCH2P{═NP(═X)(OR)2}Ph2)(CO)3] (X = O, R = Et (2a), Ph (2b); X = S, R = Et (2c), Ph (2d)) and [ReBr{κ(2)-P,N-Ph2PCH2P(═NR)Ph2}(CO)3] (R = P(═O)(OEt)2 (3a), P(═O)(OPh)2 (3b), 4-C6F4CHO (3e), 4-C6F4CN (3f), 4-C5F4N (3g)). The reactivity of the cationic complex [Re(κ(3)-P,N,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3][SbF6] (4d) has been explored allowing the synthesis of the cationic [Re(L)(κ(2)-P,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3][SbF6] (L = acetone (5a), CH3C≡N (5b), pyridine (5c), PPh3 (5d)) and the neutral [ReY(κ(2)-P,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3] (Y = Cl (6a), I (6b), N3 (6c)) complexes. The catalytic activity of complex 4d in the regioselective isomerization of terminal propargylic alcohols HC≡CCR(1)R(2)(OH) into α,β-unsaturated aldehydes R(1)R(2)C═CHCHO or ketones R(3)R(4)C═CR(1)COMe (if R(2) = CHR(3)R(4)) under neutral conditions in ionic liquids has being studied. Isolation and X-ray characterization of the key intermediate rhenium(I) oxocyclocarbene complex [Re{═C(CH2)3O}(κ(2)-P,S-Ph2PCH2P{═NP(═S)(OPh)2}Ph2)(CO)3][SbF6] (5e) seems to indicate that the catalytic reaction proceeds through tautomerization of the terminal alkynols to yield vinilydene-type species.

Task‐Specific Deep Eutectic Solvent for Selective Oxidation of Aromatic Methyl to Aldehyde

“…Under these conditions, the increased substrate-DES interaction is responsible for the enhanced oxidation of mesitylene to 3,5-dimethyl benzaldehyde. Screening the concentration of the DES study for 0.5, 1.0, 1.5, 2.0, and 2.5 mL resulted in 56, 60, 67, 86, and 86 %, respectively (Table 3, entries [12][13][14][15][16]. This gradual improvement in the yield suggests that 2 mL of DES is optimum for effective conversion.…”

“…[3,4] Francisco et al, Kudłak, and others introduced the idea of ionic liquids (ILs), which are defined as a group of organic salts with low melting points below 100°C. [5][6][7] Ionic liquids (ILs) have attracted considerable attention as reaction media [8] and catalysts [9,10] in oxidation methods, Ionic Liquids have been actively used as reaction media in transition-metal-catalyzed organic transformations [11,12] because of their high thermal, chemical, and electrochemical stability and negligible vapor pressure. [13] These properties permit ILs to be reused; however, toxicological issues and their high price pose major challenges for their use on a commercial scale.…”

SOCl2-Catalyzed Meyer–Schuster Rearrangement of 3°-Propargylic Alcohols: Synthesis of Densely Arene-Substituted Pyrazolines Bearing Quaternary Centers from α,β-Unsaturated Carbonyl Compounds and Arylhydrazines

“…However, in those cases, especially designed catalysts in which fine-tuning of steric and electronic ligands have to be maintained or in some cases reactions performed under microwave irradiation. ,, …”

Development of the Meyer–Schuster Rearrangement on Propargylic Alcohols with Fluorinated Chains

“…However, the MSR has been very rarely employed with fluorinated propargylic alcohols. Three examples described the MSR on trifluoro/perfluoro propargylic alcohols, [5a–c] while another reported the synthesis of trifluoromethylated benzothiophenes trough MSR, followed by radical cyclization [5d] …”