(Added fix recommended by Craig in comments, and complete rewrite for clarity.)
We will use the following: $\lim_{x\rightarrow 0} {\frac{\sin x}{x}}=1$.
Lemma: If $\{x_n\}$ is a sequence (of non-zero values) that converges to $0$, then $\lim_{n\rightarrow\infty}{n \sin{x_n}} = \lim_{n\rightarrow\infty} nx_n$
Proof: Rewrite $n\sin{x_n} = n x_n \frac{\sin{x_n}}{x_n}$. The lemma follows since $\sin{x_n}/x_n \rightarrow 1$ by above.
Now, let $[[x]]$ be the fractional part of $x$. Let $e_n = [[n!e]]$.
Lemma: For $n>1$, $e_n\in (\frac{1}{n+1}, \frac{1}{n-1})$
Proof: $n!e = K + \sum_{m=n+1}^\infty \frac{n!}{m!}$
Where $K$ is an integer.
But for $m>n$, $\frac{n!}{m!} = \frac{1}{(n+1)(n+2)...m} < n^{n-m}$.
So $\frac{1}{n+1}<\sum_{m=n+1}^\infty \frac{n!}{m!} < \sum_{m=n+1}^\infty n^{n-m} = \sum_{k=1}^\infty n^{-k}$
But the right hand side is a geometric series whose sum is $\frac{1}{n-1}$.
So $n!e-K\in(\frac{1}{n+1}, \frac{1}{n-1})$, and, since $K$ is an integer, it must be $e_n=n!e-K$.
Theorem: $\lim_{n\rightarrow \infty} n \sin(2\pi n! e) = 2\pi$
Proof: By periodicity of $\sin$, $\sin(2\pi n! e) = \sin(2\pi e_n)$.
Letting $x_n = 2\pi e_n$, we see, from our first lemma:
$\lim n \sin x_n = \lim n x_n$
But $nx_n = 2\pi ne_n$, and, since $ne_n\in(\frac{n}{n+1},\frac{n}{n-1})$, we see that $ne_n\rightarrow 1$. So our limit is $2\pi$.