Pyridine alkynyl lithiums

The intramolecular oxa-Michael strategy is shown in Fig. 3.22. Using pyridine as a solvent, the cw-diol 3.5a and triphosgene could react to create a carbonate product 3.48 in 85 % yield. The alkynyl lithium intermediate attacked the carbonyl group of 3.48, obtained a pair of diastereoisomer 3.47 and 3.49 which were produced depending on the different ring opening site. The main product was the... 

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

Cross-coupling with Organocopper Reagents. HexasUylbi-cyclo[2.2.2]octan-l-yl copper, prepared from tbe treatment of hexasilylbicyclo[2.2.2]octan-l-yl lithium with copper(T) iodide in THF, reacts with (iodoethynyl)trimethylsilane (eq 6) in the presence of pyridine to afford the alkynyl-substituted polysilacage compound. ... 

Olefinic aldehydes have been synthesized by a variety of methods including oxidation of the corresponding primary alcohols with the chromium trioxide-pyridine complex 195—197) or N-chlorosuccinimide-dimethyl sulfide complex 198), heating a primary alken-l-yl mesylate with dimethylsulfoxide 199), or by alkylation of the lithium salt of 5,6-dihydro-2,4,4,6-tetramethyl-l,3-(4H)-oxazine with an alkynyl iodide followed by sodium borohydride reduction and acid hydrolysis (200). 

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