documentclass{article}
usepackage{chemfig}
usetikzlibrary{positioning,calc}

begin{document}

definesubmolMe[H_3C]{CH_3}

begin{tikzpicture}[node distance=0cm and 2cm]
node (A)
  {chemfig{R-C-[::-60]O-[::-60]C-[::-60]R}};
node[above right=of A] (B)
  {chemfig{*6((-!Me)=(-!Me)-(-!Me)=(-!Me)-(-!Me)=(-!Me)-)}
};
node[below right=of A] (C)
  {chemfig{CH_3CH_2-[:-60,,3]C(-[:-120]H_3C)=C(-[:-60]H)-[:60]C{(}CH_3{)}_3}};
draw[-stealth] (A) -- ( $ (A.0)!0.5!(B.west|-A.0) $ ) |- (B.west) node[auto,pos=0.7] {i,j};
draw[-stealth] (A) -- ( $ (A.0)!0.5!(C.west|-A.0) $ ) |- (C.west) node[auto,pos=0.7] {j};
end{tikzpicture}

end{document}

documentclass{article}
usepackage{chemfig}
usepackage{etoolbox}

makeatletter
newififfork

patchcmdCF@merge@ii{-CF@full}{ifforkelse -CF@fullfi}{}{}%
% CF@merge@iii needs to be patched twice:
patchcmdCF@merge@iii{>=0]}{>=0,iffork CF@full-fi]}{}{}%
patchcmdCF@merge@iii{>=0]}{>=0,iffork CF@full-fi]}{}{}%
patchcmdCF@schemestart@i
  {letmergeCF@merge}
  {%
    defmerge{forkfalseCF@merge}%
    deffork{forktrueCF@merge}%
  }
  {}{}
patchcmdCF@schemestart@v{merge}{mergefork}{}{}

makeatother

begin{document}

schemestart
 a arrow{0} b arrow{0} c
 merge{v}(c1)(c2)(c3)--() d
schemestop

bigskip

schemestart
 a arrow{0} b arrow{0} c
 fork{v}(c1)(c2)(c3)--() d
schemestop

end{document}