14103-77-6

Since the early studies of Mannich, Mannich reaction has become an important tool for the synthesis of new compounds. Mannich bases can be either directly employed or used as intermediates. In this work, the one-carbon unit transfer reaction of tetrahydrofolate coenzyme was initiated. 1,3-Dimethylimidazolidine as a new tetrahydrofolate coenzyme model at formaldehyde oxidation level was used to react with ketone having active hydrogen atoms and amine to give the corresponding Mannich base in good yield by a covert Mannich reaction. A novel method for biomimetic synthesis of various Mannich bases is provided. 1,3-Dimethylimidazolidine as a new tetrahydrofolate coenzyme model at formaldehyde oxidation level was used to react with ketone having active hydrogen atoms and amine to give the corresponding Mannich base in good yield by a covert Mannich reaction. A novel method for biomimetic synthesis of various Mannich bases is provided. Copyright

Bis(NBH3), bis(NBF3), and NBF3/NBH3 adducts 1-3 were prepared from 1,3-dimethyl-1,3-diazolidine and characterized by the 1H, 13C, 11B, 19F, 2D 1H-13C HETCOR and NOESY NMR spectra. The structures and conformations of the adducts were established by the variable-temperature 1H NMR spectra, the X-ray diffraction method (adduct 2A), and density functional calculations at different theoretical levels. The experimental and theoretical data have revealed that bis adducts 1-3 prefer trans orientations of the borane groups (1A, 2A, 3A) in solution, the solid state, and the gas phase. The studies have shown that the energetic preference of trans adducts with respect to cis compounds, decreasing as 2A (2.9 kcal/mol) > 3A (2.7 kcal/ mol) > 1A (1.4 kcal/mol), is dictated by spatially repulsive interactions between the CH3, BH3, and BF3 groups. The results of DFT calculations agree well with an experimental trans/cis isomeric ratio of 9:1 determined in solutions of adduct 1. The calculated geometry and energy, as well as the topological analysis of electronic densities, show that trans adducts 1-3 should exist in gas phase as twist conformations T-2 stabilized by the intramolecular C-Hδ+···-δH-B or C-Hδ+···-δF-B interactions. These interactions are characterized as closedshell. The energy of one proton-hydride and proton-fluoride intramolecular contact, estimated as 1.9 (1A-T-2) and 0.7 (2A-T-2) kcal/mol, respectively, classifies the "elongated" intramolecular interactions CHδ+···-δHB and CHδ+···-δFB as weak ones. It has been established that, on going from gas phase to a condensed phase (solution and solid), the twist-conformations T-2 transform to conformations T-1, probably by intermolecular dipole-dipole interactions. The data presented in this work show that despite a weakness of the "elongated" proton-hydride and proton-fluoride interactions, they can play a significant role in the stabilization of conformational molecular states, especially when cooperativity is in action.

The development of an efficient and sustainable synthetic route for formaldehyde production from renewable feedstock, especially in combination with a subsequent transformation to straightforwardly construct valuable chemicals, is highly desirable. Herein, we report a novel manganese-catalyzed dehydrogenative cyclization of methanol as a formaldehyde surrogate with a variety of dinucleophiles for facile synthesis of N-heterocycles. The in situ generated formaldehyde via catalytic methanol dehydrogenation can be selectively trapped by diverse dinucleophiles to avoid several possible side reactions. The utility of this transformation is further highlighted by its successful application to the synthesis of 13C-labeled N-heterocycles using 13CH3OH as a readily accessible 13C-isotope reagent.

The readily synthesized and bench-stable cobalt dichloride complex (dpephos)CoCl2 is employed as a pre-catalyst for a diversity of silane additions to unsaturated organic molecules, including the normally challenging reduction of amides to amines. With regard to hydrosilative reduction of amides even more effective and activator free catalytic systems can be generated from the bench-stable, commercially available Co(acac)2 and Co(OAc)2 with dpephos and PPh3 ligands. These systems operate under mild conditions (100 °C), with many examples of room temperature transformations, presenting a first example of mild cobalt-catalyzed hydrosilylation of amides.

The C-H activation of cyclic formaldehyde aminals LCH2 (L = RNCH2CH2CH2-NR and RNCH2CH2-NR, R = Me, Et, iPr, tBu, or Ph) with S8 proceeds at unusually low temperatures (T 2S. The reaction constitutes a new, solvent-free method for the synthesis of thioureas that eliminates the toxic and highly flammable CS2. For R = tBu, the ionic carbenium thiocyanates [LCH]+ SCN- dominate the product spectrum and the respective thioureas are obtained in low yield. The reactivity of the analogous sulfur and oxygen ring systems towards S8 was investigated. 1,3-Dithiolane is cleanly converted into 1,3-dithiolane-2-thione (S8, 14 d, 190°C) and resembles the cyclic formaldehyde aminals in this respect. 1,3-Dioxolane (L = OCH2CH2O) is completely inert towards sulfur even under forceful reaction conditions (190°C, 14 d). The formation of thioureas from aminals was investigated at the CBS-4 and B3LYP/6-31G(d) levels of theory.

N-Phenyl- and N-alkyl-oxazolidines react with alkyl chlorosilanes in the presence of electron rich aromatic compounds with the formation of the expected Mannich bases: 2-methoxycarbonyl-3-methyloxazolidine also reacts with 2-methylfuran in the presence of thionyl chloride to give an a-amino acid derivative: the iminium salt derived from 1,3-dimethylimidazolidine was also shown to react with 2-methylfuran.

The condensation of α,ω-alkanediamines NH2(CN2)nNH2 with aqueous formaldehyde has been studied by NMR spectroscopy of isolated products and of product mixtures.The condensation was reversible and gave products of widely different types depending on alkane chain length: bicyclic oxadiaza compounds (n = 2, 3, 4), a tricyclic tetraaza compound (n = 2), a quinquecyclic octaaza compound (n = 3), two-dimensional polymers (n = 4, 5).A slow irreversible rearrangement gave in two cases (n = 3, 4), unicyclic 1-formyl-3-methyl-1,3-diaza compounds.The condensation of N,N'-dimethyl-α,ω-alkandediamines CH3NH(CH2)nNHCH3 with aqueous formaldehyde was also studied.The reversible formation of simple unicyclic diaza compounds was observed in all cases (n = 2, 3, 4), but in one case (n = 2) there was again a slow irreversible rearrangement to the N-formyl-N,N'N'-trimethyl derivative.The rearrangement reaction involves a hydride shift and is strictly intramolecular.The conditions for its occurrence can be understood on a conformational basis.

A series of 1,3-dialkyl-2-imidazolidinones 1 and 1,3-dialklyltetrahydro -2(1H)-pyrimidinones 2 were reduced to the corresponding aminals 3 and 4, respectively, when treated with excess lithium aluminum hydride in ether.The rate of reduction is affected dr

Amine radical cations have been generated by exposing dilute solutions of amines to 60Co γ-rays at 77 K.They are well characterised by their e.s.r. spectra, the method and interpretation being established by showing that the e.s.r. data for Me3N(.+) cations are indentical with literature values.Results for the triethylammonium cation show that the β-protons do not occupy the most favourable sites for maximum hyperconjugation, in contrast with other radical cations.This is explained in terms of steric factors, and an equilibrium between two preferred conformations. 1,1-Diamines, R2NCH2NR2, give cations having localised structures, R2N(.+)CH2NR2, rather than the delocalised structure adopted by acetal cations.Possible evidence for weak N-N bonding and delocalisation is adduced for NN'-dimethylpiperazine cations, but we confirm that the cation of triethylenediamine has a truly delocalised ?(*) structure.There is no tendency for R3N(+.) cations to react with neutral amines to give ( dimer cations, in marked constrast with results for corresponding trialkylphosphine systems.