Other Acetylene Reactions of Mechanistic Interest

Other Acetylene Reactions of Mechanistic Interest.—Several recent papers have been concerned with thermal rearrangements of acetylenes. c/ -Hexa-1,5-diyn-3-ene (187) on gas-phase pyrolysis in a flow system at 300 °C undergoes a de nerate thermal rearrangement. Thus pyrolysis of the dideuteriated analogue (188) results in scrambling of the deuterium between acetylenic and 

Thermolysis of rm jr-diethynylcyclopropane (192) is pressure dependent. At 100 Torr and 250 only (193) is produced but (194) and (195) become the major products as the pressure is reduced.  

Low-pressure (10 —10 Torr) gas-phase pyrolysis ( 650°C) of 3-phenylpropargyl acetate or benzoate (196) gives the corresponding alkyl or aryl phenyl-2-methylene-l,3-dione (197) in good yieldthe proposed 

The detailed mechanism of the rearrangement of C-labelled acrylates [(207) and (208)] and the corresponding carbenoid precursors [(209) and 

A side-reaction occurring in the Wolff-Kishner reduction of certain acetylenic aldehydes [(213) (214)] is believed to be the result of two successive 

---