Make a seven-column matrix:
\documentclass{article}
\usepackage{amsmath}
\usepackage[all,cmtip]{xy}
\begin{document}
\[
\xymatrix@C-1pc{
& B' \ar[rr]^{t_i} && H \ar[rr]^i && B \ar[dr]^{\tilde{v}} \\
E'_{n+1} \ar[ur]^{t_{\tilde{w}}} \ar[rr]_{t_{j_n}} &&
E'_n \ar[rr]_{\bar{u}} && E_n \ar[rr]_{j_n} && E_{n+1}
}
\]
\end{document}
The instruction @C-1pc
reduces the space between columns.

With the missing arrows:
\documentclass{article}
\usepackage{amsmath}
\usepackage[all,cmtip]{xy}
\begin{document}
\[
\xymatrix@C-1pc{
& B' \ar[rr]^{t_i} && H \ar[rr]^i \ar[dr]^v && B \ar[dr]^{\tilde{v}} \\
E'_{n+1} \ar[ur]^{t_{\tilde{w}}} \ar[rr]_{t_{j_n}} &&
E'_n \ar[rr]_{\bar{u}} \ar[ur]^{t_w} && E_n \ar[rr]_{j_n} && E_{n+1}
}
\]
\end{document}

With tikz-cd
:
\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz-cd}
\begin{document}
\[
\begin{tikzcd}[column sep=small]
& B' \arrow[rr,"t_i"] && H \arrow[rr,"i"] \arrow[dr,"v"] &&
B \arrow[dr,"\tilde{v}"] \\
E'_{n+1} \arrow[ur,"t_{\tilde{w}}"] \arrow[rr,"t_{j_n}"'] &&
E'_n \arrow[rr,"\bar{u}"'] \arrow[ur,"t_w"] && E_n \arrow[rr,"j_n"'] &&
E_{n+1}
\end{tikzcd}
\]
\end{document}

Labels are by default typeset on the left of the arrow (think to rivers), but with "<label>"'
(note the apostrophe) the label goes on the other side. Alternatively, precede the label with the keyword swap
.
\[...\]
instead of$$...$$
suggestion – Sebastiano Jan 2 at 20:22