Quaternarization

A relative of the latter class of compounds are the macrotricyclic quaternary ammonium salts which have been reported by Schmidtchen. The bridges may contain either methylenes or ethyleneoxy units and the nitrogens are quaternarized. The underlying principle is to provide a cavity suitable for solvating or at least trapping anions. Schmidtchen presents evidence which suggests the formation of halide inclusion complexes. The synthesis of these molecules is accomplished along more or less traditional lines Such a species is illustrated above as compound 19. 

RajanBabu reported the first preparation of a bis-imidazolium salt 15 bearing a chiral linker (Scheme 11). The starting material was the enantiomerically pure (S)-l,l -bi-2-naphtol bis(trifluoromethanesulfonate) which was transformed in two steps into the dibromomethyl derivative 16 and then into the bis-imidazole. Quaternarization of this compound afforded 15 [20]. 

Quaternarization of 43 with phenacyl bromide produced the corresponding salt 51 that was reacted with several triple-bond-containing dipolarophiles (Scheme 4), such as dimethyl acetylenedicarboxylate (DMAD) or alkyl propiolates to give tricyclic compounds 52, 53 and 54, 55. Compound 51 reacted also with acrylonitrile as dipolaro-phile in MeCN/K2C03 to give the cycloadduct 56 as a mixture of diasteroisomers. 

Trobably, partial desilylation has occured through quaternarization of the nitrogen atom of the MSMA with chloride (see Section V). 

Phenothiazines are tranquilizing drugs in wWch the basic structure consists of two benzene rings fused to a central six-membered ring containing a sulfur and a nitrogen. They are sometimes administered as the hydrochloride salt by quaternarization of the side chain nitrogen. 

Anchoring polymers are prepared from chloromethylated styrene-divinylbenzene copolymers of either 1 equiv Cl/g or 4 equiv Cl/g capacity. These resins arc stirred for 24 h in refluxing CHC13, with either 1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine, or TMEDA. The polymers are filtered off, washed with ClIClj, acetone and Et20, then dried overnight under vacuum at 25 °C. Nitrogen elemental analysis and chloride ion titration gives a value of 80-90% quaternarization. 

The Hofmann degradation of quaternary ammonium hydroxides, which has been used in the preparation of olehns has also been occasionally applied to the synthesis of acetylenes, as shown in equations (94)-(96). Quaternarized enamines are also used... 

As mentioned above, the quaternarization method using N-silylmethyl-imines [Eq. (2)] offers an even more general and convenient method of azomethine ylide generation than the original N-silylmethylation method shown by Eq. (1). Another advantage is the ready availability of N-silylmethylimines, which are conveniently prepared by the condensation of carbonyl compounds with silylmethylamine or with silylmethyl azide in the presence of triphenylphosphine (84JOC2688). 

To improve the sensitivity of the pilocarpine analysis - enabling determinations in biological fluids - Mitra et al.7 developed a derivatization technique by means of which pilocarpine was quaternarized with the aid of -nitrobenzylbromide (0.25 mg/ml - 24 hrs at 40°C). The quaternary derivatives were analyzed on an octadecyl column using 0.001 M sodium octane-sulfonate in methanol - water (4 1) as mobile phase, the derivatization technique described was also applicable to other amines. 

In most cases, the sulfoxides produced after the asymmetric transformation are reduced with sodium or aluminium amalgam, or Raney nickel. The sulfoxide may also be reduced by LiAffl into a sulfide, winch after quaternarization becomes a leaving group [474], If the carbon skeleton of the substrate bears appropriate substituents, the sulfoxide can suffer [2,3] sigmatropic rearrangements [497, 498] or Pummerer rearrangements. In all these types of applications, the chiral auxiliary is never recovered. 

Bei der Alkylierung von 1-Alkyl-1 H- oder 2-Alkyl-2H-indazolen entstehen quaternare 1,2-Dialkyl-indazolium-Salze. Dabei resultiert sowohl aus 1-Methyl-lH- als auch aus 2-Methyl-2H-indazol dasselbe 1,2-Dimethyl-indazolium-iodid273. Wahrend in der alteren Literatur die Umsetzung der isomeren N-Methyl-indazole mit Methyliodid bei 100° und mehrstundigem... 

Bei der Hydrolyse von Piperidinium--5-nitro-lH-indazolium-3-olat zeigt sich, daB das quaternare N-Atom eine gute Abgangsgruppe ist und es zur Bildung von 5-Nitro-2-methoxy-benzoesdure-piperidinoamid363 kommt. 

Figure B8.1. a, b) Static distortion of carbonyl group to favor overlap with the highlighted bonds. The bonds in a) are poorer n donors because of electrostatic effects of the quaternar y N center and interaction with Thus interaction (6) is favored, (c) Distortion in the transition state to favor...

In 1999, the group of Roucoux studied a new series of easily synthesized ionic surfactants that efficiently stabilize active suspensions of rhodium colloids in the hydrogenation of arenes in a biphasic Uquid-Uquid medium [34-36]. The synthesis of N,N-dimethyl-N-alkyl-N-(2-HydroxyEthyl)Ammonium salts which provide an electrosterical stabilization has been obtained by one step quaternarization of N,N-dimethylethanolamine with the appropriate functionaUzed alkanes or by ion exchange. These salts HEA-CnX bear an alkyl chain containing n= 12-18 carbon atoms and can be prepared with various counter-anions X such as Br, Cl, 1, CH3SO3, BF4 (Scheme 11.2). 

We studied the capacity of dendrimers 36-[G ] and 37-[G ] (n generation) (Scheme 26) to mediate the in vitro delivery of nucleic acids (pCMV-luc plasmid, luciferase gene) into mammalian cells (3T3 cells). The property expected in this case is the self-assembly of the cationic dendrimer with the gene bases, which would mediate the penetration of the gene within the cell. The results obtained strongly depend on the type of end groups, even if 36-[G ] and 37-[G J differ only by the type of agent used to induce the quaternarization of the terminal amines. Indeed, the methylated forms 37-[G ] were found to be rather tox-... 

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