$\left. \begin{gathered}
  (A)\,\,\xrightarrow{{PB{r_3}}}\,(C)\,\xrightarrow{{Mg\,,\,ether}}Grignard\,\,reagent \hfill \\
  (A)\,\,\xrightarrow[{{H_2}S{O_4}}]{{N{a_2}C{r_2}{O_7}}}\,(B) \hfill \\ 
\end{gathered}  \right\}$  $ \to \,(D)\xrightarrow{{{H_3}{O^ \oplus }}}$  $(3,4-$ ડાયમિથાઇલ $3-$  હેકઝાનોલ l$)$