(figure) $\xrightarrow[{(2)\,Zn}]{{(1)\,{O_3}}}\mathop {\begin{array}{*{20}{c}}
{\,\,\,\,O\,\,\,\,\,\,\,O\,\,} \\
{\,||\,\,\,\,\,\,\,\,\,||} \\
{H - C - C - H}
\end{array}}\limits_{Glyoxal} + $ $\mathop {\begin{array}{*{20}{c}}
{\,\,\,O\,\,\,\,\,O\,\,} \\
{\,||\,\,\,\,\,\,\,\,||} \\
{C{H_3} - C - C - C{H_3}}
\end{array}}\limits_{2,3 - Bu\tan edione} + \mathop {\begin{array}{*{20}{c}}
{\,\,\,\,\,\,O\,\,\,\,\,O} \\
{\,\,\,\,\,\,||\,\,\,\,\,\,||} \\
{C{H_3} - C - C - H}
\end{array}}\limits_{Pyrualdehyde} $
$C{{H}_{3}}\,-\,\,\overset{\overset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{C}}\,H\,\,-\,\,C{{H}_{3}}(excess)\,\,+\,\,B{{r}_{2}}\,\xrightarrow{hv}$
$\,\,\,\,C{{H}_{3}}\,-\,\,\overset{\overset{C{{H}_{3}}}{\mathop{|}}\,}{\mathop{\underset{\underset{Br}{\mathop{|}}\,}{\mathop{C}}\,}}\,\,\,-\,\,C{{H}_{3}}\,+\,\,C{{H}_{3}}\,-\,\,CH\,\,-\,\,C{{H}_{2}}\,-\,\,Br$