Hexynes

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Addition of n butyl bromide then gives M-butylacetylene (1-hexyne) ... 

A suspension of di1ithiohexyne in diethyl ether was made from 0.20 mol of 1-hexyne and 0.5 mol ethyllithium in 400 ml of diethyl ether in the same way as described for 1-heptyne (see this chapter, Exp. 27). The suspension was cooled to -40°C and at this temperature a solution of 0.20 mol of ethylene oxide in 50 ril of diethyl ether was added in 15 min, the brown colour changing into yellow. Subsequently the temperature was allowed to rise graduallyduring 1 h to +5°C. 

To a solution of ethylnagnesium bromide in 350 ml of THF, prepared from 0.5 mol of ethyl bromide (see Chapter 11, Exp. 6) was added in 10 min at 10°C 0.47 mol of 1-hexyne (Exp. 62) and at 0°C 0.47 mol of trimethylsilylacetylene (Exp. 31) or a solution of 0.60 mol of propyne in 70 ml of THF (cooled below -20°C). With trimethyl si lylacetylene an exothermic reaction started almost immediately, so that efficient cooling in a bath of dry-ice and acetone was necessary in order to keep the temperature between 10 and 15°C. When the exothermic reaction had subsided, the mixture was warmed to 20°C and was kept at that temperature for 1 h. With 1-hexyne the cooling bath was removed directly after the addition and the temperature was allowed to rise to 40-45°C and was maintained at that level for 1 h. 

I-Hexyne and allyl carbonate undergo dimerization-allylation to give (Z)-5-allyl-4-butyI-l,4-undecadien-6-yne (765) in 85% yield[475]. 

The carbonylation of 2-methyl-3-butyn-2-oI (50) in benzene gives teraconic anhydride (51). Fulgide (53) (a dimethylenesuccinic anhydride derivative), which is a photochromic compound, can be prepared by the carbonylation of 2,5-dimethyl-3-hexyne-2,5-diol (52)[21], The reaction proceeds under milder conditions when PdlOAc) is used as a catalyst in the presence of iodine [23],... 

Butyl-5-methyl 2-Bromo-5-methylacetanilide l-(Tri-n-butyl-stannvl)hexyne, (1) Pd(PPh,)4, (2) PdCl lCHjCN) 81,77 [1]... 

Show by writing appropriate chemical equations how each of the following compounds could be converted to 1 hexyne... 

Wnte the structure of the major organic product isolated from the reaction of 1 hexyne with... 

The alkane formed by hydrogenation of (S) 4 methyl 1 hexyne is optically active but the one formed by hydrogenation of (S) 3 methyl 1 pentyne is not Explain Would you expect the products of hydrogenation of these two compounds in the presence of Lindlar palladium to be optically active" ... 

Write the equation for the reaction of 1 hexyne with ethyl magnesium bromide as if it involved ethyl anion (CH3CH2 ) instead of CH3CH2MgBr and use curved arrows to represent the flow of electrons j... 

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