Displacement trimethylamine

The tripod ligand tris(2-dimethylaminoethyl)amine (Meetren) also displaces trimethylamine from [MCU(NMe3)2] yielding 1 1 adducts MCU-Meetren (M = Zr or HQ. On the basis of IR and HNMR data these compounds have been formulated as [MCl2 Me6tren ]Cl2 salts in which Mcetren behaves as a tetradentate ligand. Unfortunately, conductance studies proved unreliable. 

It is often advantageous to proceed to a desired product through two nucleophilic displacements rather than directly when one can exploit a difference in the reactivity of two leaving groups. An example is the conversion of 4-chloro-2,6-dimethoxypyrimidine (109) (not satisfactorily reactive with sulfanilamide anion) by means of trimethylamine into the more reactive trimethylammonio derivative 110. Conversion of chloro-quinohnes and -pyrimi-dines into nitriles is best accomplished by conversion (with sulfite) into the sulfonic acids before reaction with cyanide. 

Reaction of [Pt3(/u-S02)3 P(Cy)3 3] with 2,6-xylyl isocyanide results in displacement of one or at most two of the S02 ligands by the isocyanide.21 Similarly, carbon monoxide usually only partially displaces the S02, but the addition of trimethylamine /V-oxide (Me3NO) facilitates the substitution leading to formation of [PtsQx-COjsfPlCyjs js].22 Me3NO also facilitates substitution of one S02 ligand by halides and azide.2... 

The behavior of the aldehyde complex toward Lewis bases was examined. The acetaldehyde moiety in the acetaldehyde complex Me2A10CPhNPh MeCHO was not displaced by a large excess of Lewis base such as pyridine or tetrahydrofuran, but was replaced by a strong electron donor substance such as trimethylamine oxide to give a crystalline trimethylamine oxide complex, Me2A10CPhNPh ONMe3, which is identical to that obtained from trimethylamine oxide and [Me2AlOCPhNPh]2. 

Wu et al. (5) recently interpreted the thermal decomposition mechanism of tetramethylammonium-exchanged Y zeolite. The order of occurrence of the gaseous decay products is (mole %) (CH N (50), CH4 (11), (CH3)20 (10), CO (9), CH3OH (6), H2 (4), C4H8 (4), C2H4 (trace), for the decomposition carried out at 275°C under vacuum. At this temperature, a displacement reaction of water nucleophile on the tetramethyl cation, forming methanol and trimethylamine, is proposed ... 

The abnormal displacement of trimethylamine from the 2-pyrrolylmethylammonium salt (149) by cyanide ion to give 2-cyano-l,5-dimethylpyrrole (151) (77JOC1096), in amanner which has also been observed with analogous reactions of furan derivatives, probably occurs via an SN2 mechanism, although the dependence of relative yield of (151), compared with the normal Sn2 product (150), upon the solvent and the counter anion does not rule out the possibility of the initial formation of the pyrrolylmethyl cation. The highest yield of (151) was achieved when the reaction was conducted upon the chloride salt in DMSO and, in most reactions, dipyrrolylmethanes were also formed. 

A spiro indoline (347) has been isolated from the reaction of the quaternized derivative of 5-methoxy-l-methyl-3-(2-dimethylaminoethyl)indole with lithium in liquid ammonia in the absence of a proton donor (68TL81). The product presumably arises from the rapid sequential addition of two electrons to generate the dianion of the tryptamine, which facilitates the nucleophilic displacement of trimethylamine. Reduction in the presence of methanol produces the 4,7-dihydrotryptamine (see Section 3.05.1.5). 

Tris(3-cyanomethyl-2,4-pentanedionato)chromium(III), [Cr H8CC(0)C(CH2CN)C(0)CH, 3]> has recently been prepared by the aminomethylation of tris(2,4-pentanedionato)-chromium(III) followed by quaternization of the amine and subsequent displacement of trimethylamine with alkali metal cyanide.1 The procedure described below is a modification of... 

The gas-phase base-induced elimination reaction of halonium ions was thoroughly investigated in radiolytic experiments22. Radiolytically generated acids C/JH5+ (n = 1,2) were allowed to react at 760 Torr with selected 2,3-dihalobutanes to form the halonium intermediates which, in the presence of trimethylamine, undergo base-induced bimolecu-lar elimination as shown in Scheme 6. This elimination reaction occurs in competition with unimolecular nucleophilic displacement to the cyclic halonium ion and subsequent rearrangement. Isolation and identification of the neutral haloalkenes formed and kinetic treatment of the experimental results indicated that 3-halo-1 -butene is formed preferentially with respect to the isomeric 2-halo-2-butenes and that the bimolecular elimination process occurs predominantly via a transition state with an anti configuration22. 

The dialkylamino group of a 2-dialkylaminomethyl pyrrole can also be displaced by various nucleophiles. In a typical example, displacement of trimethylamine from the quaternary salt derived from the Mannich base of a 1-arylpyrrole gives an azide which can be reduced to give the aminomethylpyrrole (Scheme 129). 

Hi. Synthesis of species containing ligands which can be displaced more easily than CO. This is also an extension of the technique employed to activate Os3(CO)i2 and has been widely used in Osg chemistry. When oxidative displacement of carbon monoxide from Osg(CO)i8 and Os5(CO)ig by trimethylamine oxide is carried out in the presence of acetonitrile, the substituted products Osg(CO)i7(MeCN), Osg(CO)ig(MeCN)2 (97,118), and Oss(CO)i s(MeCN) (92) are isolated in good yields. The acetonitrile derivatives of the raft Osg(CO)2i species Osg(CO)(2i )(MeCN) (n = 1,2) have alternatively been synthesized by condensation of Os3(CO)io(MeCN)2 using PdCl2 (99). 

In a similar manner, toluene-p-sulfonate derivative of alcohols on nucleophilic displacement with trimethylamine N-oxide followed by treatment with a base gives the carbonyl compound and trimethylamine. 

Less brutal approaches to displacement of CO ligands have provided the opportunity for designed syntheses. The most successM approaches are (1) the use of trimethylamine N-oxide to convert a bound CO ligand to CO2, (2) the use of one-electron oxidation or reduction to generate more labile (see Labile) cluster radical intermediates, and (3) the use of nucleophiles (see Nucleophile), such as halide ions, to promote CO dissociation. 

Since direct substitution of 4-chloroquinazolines with cyanide without a suitable catalyst has no preparative value (cf. p 131), displacement of the 4- or 2-trimethylammonium group in 1 with cyanide using potassium cyanide or tetraethylammonium cyanide is the most convenient method for the preparation of quinazoline-4-carbonitriles 2B and quinazoline-2-carbonitriles 2A, respectively. Trimethylquinazolinylammonium chlorides are easily obtained from respective chloroquinazolines and trimethylamine. ... 

For the synthesis of guanine acyclonucleosides a facile two-step displacement at C6 using a mixture of trimethylamine and tetraethylammonium hydroxide in aqueous 1,2-dimethoxyethane (monoglyme) to give 12 has been described. ... 

Chloropurines are less reactive and the displacement with cyanide under these conditions was unsuccessful. However, the use of tetraethylammonium cyanide with trimethylamine as catalyst allows this conversion to be carried out very readily at room temperature an example is the formation of 7. ... 

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