1- Propyne, 1-ethoxy

Alkynes with EWGs are poor substrates for the coupling with halides. Therefore, instead of the inactive propynoate, triethyl orthopropynoate (350) is used for the coupling with aryl halides to prepare the arylpropynoate 351. The coupling product 353 of 3,3-dicthoxy-l-propyne (352) with an aryl halide is the precursor of an alkynal[260]. The coupling of ethoxy) tributylstan-nyl)acetylene (354) with aryl halides is a good synthetic method for the aryl-acetate 355[261]. 

Some studies seeking preferred conditions for this reaction have been reported. Optimum yields of 1-ethoxy-1-propyne and 1-ethoxy-l-butyne are found when the product is worked up before allowing the ammonia solvent to evaporate, as the product evidently volatilizes with the ammonia. An experiment with 1-ethoxy-1-propyne showed a marked increase in yield when ammonia predried over calcium hydride was used instead of ammonia directly from the cylinder. A twofold excess of ethyl bromide is required to obtain a good yield of l-ethoxy-l-but5me, since elimination apparently competes with alkylation in this case. 

Ethoxy-2-propyne, 1909 f Ethyl isopropyl ether, 2012 f Ethyl propenyl ether, 1956 f Ethyl vinyl ether, 1610... 

With the aid of 13C NMR, 6Li NMR and XH HOESY (heteronuclear Overhauser effect spectroscopy) NMR of a-lithiomethoxyallene (106) and l-lithio-l-ethoxy-3-J-butylallene (107) as well as by ab initio model calculations on monomeric and dimeric a-lithiohy-droxyallene, Schleyer and coworkers64 proved that 106 and 107 are dimeric in THF (106 forms a tetramer in diethyl ether) with a nonclassical 1,3-bridged structure. The 13C NMR spectrum of allenyllithium in THF is also in agreement with the allenic-type structure the chemical shift of C2 (196.4 ppm) resembles that of neutral allene (212.6 ppm), rather than C2 of propyne (82.4 ppm). 

Saccharin pseudochloride 112 (R = C1) reacts with 1-diethylamino-l-propyne to give 113. When the corresponding 3-ethoxy derivative 112 (R = OEt) was treated with the same alkyne, a ring-expansion product 114 (R = OEt) was isolated. On the other hand, the analogous thiazepine 114 (R = OSiMc3) is obtained, together with the ketone derived by hydrolysis of the silyl enol ether, by the reaction of saccharin with BuLi/trimethylsilyl chloride (TMCS)... 

Reactions. - Photoreactions. 3-Phenyl-1,2-benzisothiazoles (21 X=H, Cl) and electron-rich alkynes (ethoxyacetylene, ethoxy-propyne, and diethylaminopropyne) undergo photocycloaddition to give substituted 3>4-benzo-2,6-thiazabieyclo[3 2.0Jhepta-3,6-dienes (22 R=H,CHj,R =0Et R=NEt2,R =CH, respectively), and smaller amounts of other products. 1,4-Benzothiazepine... 

The a-silylmethyl esters (252), potentially useful as precursors to ot-methylene esters can be prepared by additions of l-ethoxy-3-trimethylsilyl-l-propyne to a wide variety of both saturated and... 

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