Consider the synthetic sequence shown. Identify the reagents for all three steps. Draw the structures of organic compounds A and $B.$ Omit byproducts.

Identify reagent $1.$

reagent $1$

Draw compound $A.$

$\backslash$table$[[$Select$,$Dran,,lates,Mo$,,,$Erase$],[\frac{?}{?},//,$III,c$,H,Mg,Br,.]]$