New Routes to β-Iminophosphonates,Phosphineoxides, and Sulfides

Abstract

Two synthetic methods leading to β-iminophosphonates, phosphineoxides, and sulfides 2 are reported. The first method involves the reaction of imines with chlorophosphines and phosphites followed by oxidation or sulfurization. The second one utilizes the reaction of imines with diethylchlorophosphate and thiophosphate. The stereochemistry of the obtained products is discussed, and their structure is confirmed by NMR (¹H, ³¹P, ¹³C) and IR spectroscopies, and by mass spectrometry.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT      

An air-stable chiral Hf-based catalyst for asymmetric Mannich-type reactions

A new class of isolable, air-stable, storable, and Hf-based catalyst has been developed. In the presence of 10 mol % of the powdered Hf catalyst, the asymmetric Mannich-type reactions of imines with silicon enolates derived from esters proceeded smoothly to afford the corresponding Mannich-type adducts in high yields with high enantioselectivities. Hafnium single crystals for X-ray analysis were obtained, and the crystals also showed high performance in the asymmetric Mannich-type reactions.     

Zwitterionic adducts from addition of imines to the α-carbon atom of pentacarbonyl(vinylidene)chromium and -tungsten complexes

Imines, Im, such as MeN=C(Ph)H (5), 2-methyl 4,5-dihydrothiazole (8a), 2-methyl 4,5-dihydrooxazole (8b) and MeN=C(OMe)Me (13) add to the α-carbon atom of the vinylidene ligand in [(CO)₅Cr=C=CMe₂] (4) to give isolable zwitterionic adducts, [(CO)₅Cr⁻–C(=CMe₂)(Im⁺)]. The reaction of [(CO)₅W=C=CPh₂] (12) with 13 also yields an adduct, [(CO)₅W⁻–C(=CPh₂){NMe=C(OMe)Me}⁺] (15), whereas from the corresponding reaction of 4 with xanthylideneimine, H–N=C(C₆H₄)₂O (16), a carbene complex, [(CO)₅Cr=C(i-Pr)–N=C(C₆H₄)₂O] (17), is obtained. Complex 17 presumably is formed by initial addition of 16 to 4 and subsequently rapid rearrangement. In solution, the adduct [(CO)₅Cr⁻–C(=CMe₂)(NMe=C(Ph)H)⁺] (6) slowly cyclizes to form the 2-azetidin-1-ylidene complex [(CO)₅Cr= Me₂] (7). In contrast, when solution of those zwitterions are heated that are formed by addition of 4,5-dihydrothiazole or 4,5-dihydrooxazole to 4, no cyclization is observed but rather the formation of 4,5-dihydrothiazole and 4,5-dihydrooxazole complexes, respectively. The structures of two adducts, [(CO)₅Cr⁻–C(=CMe₂)(Im⁺)] (Im=MeN=C(Ph)H, 2-methyl 4,5-dihydrothiazole) and of the substitution product [(CO)₅W(2-methyl 4,5-dihydrothiazole)] have been established by X-ray structural analyses.     

Novel versatile imine—enamine chemosensor based on 6-nitro-4-oxo-4H-chromene for ion detection in solution, solid and gas-phase: synthesis, emission, computational and MALDI-TOF-MS studies

A new versatile emissive molecular probe (3) derived from 1,5-bis(2-aminophenoxy)-3-oxopenthane bearing two units of 6-nitro-4-oxo-4H-chromene- has been prepared by a Schiff-base condensation method using conventional and green, ultrasound-aided, methods. The dry yellow powder was characterized as the imine species (3). These imine species, however, where found to rapidly convert to their enamine form (4) in solution, under the presence of water traces. This reaction was computationally studied through Density Functional Theory (DFT) in order to investigate the relative stability of the molecular pair 3/4. The sensing properties of the enamine (4) towards various metal ions were investigated via absorption and fluorometric titrations in solution in dichloromethane, acetonitrile and DMSO. The compound shows a fluorescent turn-off response in the presence of Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Ag⁺ over the other metal ions studied, such as Li⁺, Na⁺, K⁺, Ca²⁺, Co²⁺ and Ni²⁺, being stronger for Cu²⁺ and Hg²⁺. The gas phase chemosensing abilities of (3) were also explored suggesting (3) as new active MALDI-TOF-MS matrix by two dry methods showing a strong selectivity towards Cu²⁺ and Ag⁺. Our preliminary results show promising uses of (3) supported in PPMA films as metal ion solid chemosensor.     

Synthesis of 2-amino-1,3-dienes by chromium-catalyzed addition of silylated propargyl bromides to imines

(Silyl)methylallenic amines were synthesized by the chromium-catalyzed addition of (4-bromobutynyl)trimethylsilane to tosyl imines. Regioisomeric mixtures of the desired allene and the corresponding alkyne were obtained. Allenic imines were then treated with TBAF to afford 2-aminomethyl-1,3-dienes in good yields (62-92%). In the presence of a Lewis acid, silylallenic imines were added to benzaldehyde dimethylacetal to give highly functionalized dienes with excellent yields and good to excellent diastereomeric ratios.     

Simple manganese carbonyl catalyzed hydrogenation of quinolines and imines

Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese. Herein, we describe the hydrogenation of quinolines and imines catalyzed by simple manganese carbonyls, Mn₂(CO)₁₀ or MnBr(CO)₅, thus eliminating the prerequisite pincer-type or bidentate ligands.     

Iridium-catalyzed asymmetric hydrogenation of imines in supercritical carbon dioxide using phosphite-type ligands

A series of chiral phosphite-type ligands has been evaluated in the iridium-catalyzed asymmetric hydrogenation of acyclic arylimines in supercritical CO₂. High reactivities (100% conversion in 50-120 min) and enantioselectivities (up to 95%) were obtained.     

An economic and efficient tetrahydrofuranylation of alcohols, imines and alkynes

The tetrahydrofuranyl radical, generated by heating tetrahydrofuran in the presence of air and allyl or benzyl chloride, becomes a useful tool in order to transform the hydroxyl functions into ethers, or the CN double bond into amine, or the C-C triple bond into vinyl derivatives. A radical mechanism is proposed followed by a nucleophilic substitution for the alcohol substrate and a radical addition for the iminic and the acetylenic reactants.     

Fixation of Metallo Nitrile Ylides and Metallo Nitrile Imines as Ligands in Transition Metal Complexes [1]

1,3‐Dipoles of the type metallo nitrile ylide and metallo nitrile imine were prepared by mono‐α‐deprotonation of CH‐acidic {[W(CO)₅CHCH₂PPh₃]PF₆, M(CO)₅CNCH₂CO₂R (M = Cr, W; R = Me, Et), [Pt(Cl)(CNCH₂CO₂Et)(PPh₃)₂]BF₄} and NH‐acidic isocyanide complexes (Cr(CO)₅CNNH₂) and were stabilized by coordination to a second transition metal complex fragment {Cr(CO)₅, [M(CO)₅]⁺ (M = Mn, Re), [FeCp(CO)₂]⁺, [Pt(Cl)(PR₃)₂]⁺ (R = Et, Ph)}. All dinuclear products 1 – 7 , 10 , and 11 are neutral species except [(Ph₃P)₂(Cl)Pt{μ₂‐CNCH(CO₂Et)}Pt(Cl)(PPh₃)₂]BF₄ ( 8 ). Complex (OC)₅W{μ₂‐CNCH(CO₂Et)}Pt(Cl)(PEt₃)₂ ( 5b ) was characterized by X‐ray diffraction. Twofold deprotonation/platination to give (OC)₅Cr{μ₃‐CNC(Ph)}[Pt(Cl)(PPh₃)₂]₂ ( 9 ) was achieved in the case of Cr(CO)₅CNCH₂Ph.     

Catalytic asymmetric synthesis of α-(trifluoromethyl)benzylamine via cinchonidine derived base-catalyzed biomimetic 1,3-proton shift reaction

Here we describe catalytic asymmetric synthesis of α-(trifluoromethyl)benzylamine (1) via biomimetic transamination using chiral base. Imine 4 was isomerized to Schiff base 5 using 50 mol.% of cinchonidine derivatives as a catalyst in chloroform, methanol or acetonitrile. In the case of cinchonidine 6 as a catalyst, the reaction conducted in chloroform allowed for 79% conversion of the starting imine 4 in 52 days. The product imine 5 was obtained of (R) absolute configuration in 35% ee as individual compound without any byproducts. The catalyst 6 can be recovered (>95%) by adding n-hexane to the reaction mixture followed by a simple filtration.