Acetylene derivatives quaternary

Condensation of the acetylenic compound (173) with formaldehyde and di-ethylamine, catalysed by copper(ii) acetate, gave the diethylaminomethylacetylene (174) 186 derived quaternary salt undergoes an interesting cyclization (see p. 290). 

Acetylene derivatives from enamines via quaternary enammonium salts... 

Asymmetric conjugate addition of a-substituted-oc-cyanoacetates 77 to acetylenic esters under phase-transfer conditions is somewhat of a challenge, because of the difficulty encountered in controlling the stereochemistry of the product. In addition, despite numerous examples of the conjugate additions to alkenoic esters, no successful asymmetric conjugate additions to acetylenic esters have been reported to date. In this context, Maruoka and coworkers recently developed a new morpholine-derived phase-transfer catalyst (S)-76 and applied it to the asymmetric conjugate additions of a-alkyl-a-cyanoacetates 77 to acetylenic esters, as indicated in Table 5.11 [40], In this asymmetric transformation, an all-carbon quaternary stereocenter can be constructed with a high enantiomeric purity. 

N-Alkylation—Secondary Mannich bases can give the corresponding tertiary derivatives by treatment with particular alkylation agents, such as epoxides (affording P-ami-noalcohols) and acrylic derivatives. Tertiary Mannich bases, mostly, are submitted to N-alkylation in order to produce stable quaternary ammonium salts to be subsequently subjected to deamination (Sec. A.2). However, different quaternary ammonium byproducts can be readily given by the reaction. " For instance, a base-catalyzed rearrangement is afforded by allyl ammonium salts 365 (Fig. 144), obtained by N-alkylation of acetylenic Mannich bases with ally] halides. " In the presence of sodium hydride, the compounds 365 yield a wide range of 3-amino-5-hexen-l-yne derivatives 366. 

Horner et al. have studied the mechanisms by which onium compounds inhibit steel corrosion. Kichigin et al. studied tetra-n-butylammonium cation (TBA ) and other quaternary nitrogen compounds in the presence of iodide, and Aramaki et al. studied TBA+ in the presence of halides, SOj", SCN , SH , NOJ, and N3. In all these cases, halides were shown to be necessary for good inhibitor performance and the observed behavior was consistent with competitive co-adsorption of ion pairs (side by side). Sulfonium derivatives also require the presence of halide ions and, likewise, apparently co-adsorb to form ion pairs on the surface. As discussed below, unsaturated oxygen compounds, such as aldehydes and acetylenic alcohols, also require a halide ion for good performance. 

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