Add old-to-new domain redirect into existing redirect rules in web.config for IIS

I have a multi-domain website which does some common redirects for things like enforcing https and www and trailing slashes. The code in web.config is as follows:

<rewrite>
<rules>
<rule name="Redirect to https" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
<match url="*" negate="false" />
<conditions logicalGrouping="MatchAny">
<add input="{HTTPS}" pattern="off" />
</conditions>
<action type="Redirect" url="https://{HTTP_HOST}{REQUEST_URI}" redirectType="Permanent" />
</rule>
<rule name="Redirect - Top domains with non-www to www" stopProcessing="true">
<match url="^_*(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false">
<add input="{HTTP_HOST}" pattern="^([^\.]+)\.([^\.]+?)$" />
</conditions>
<action type="Redirect" url="{MapSSL:{HTTPS}}www.{HTTP_HOST}/{R:1}" redirectType="Permanent" />
</rule>
<rule name="Add trailing slash" stopProcessing="true">
<match url="(.*[^/])$" />
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
<add input="{URL}" pattern="/umbraco_client" negate="true" />
<add input="{URL}" pattern="/setsquare" negate="true" />
<add input="{URL}" pattern="/install" negate="true" />
<add input="{URL}" pattern=".axd" negate="true" />
<add input="{URL}" pattern=".webmanifest" negate="true" />
<add input="{URL}" pattern="/signin-google" negate="true" />
<add input="{URL}" pattern="/assets" negate="true" />
</conditions>
<action type="Redirect" url="{R:1}/" />
</rule>
</rules>
<rewriteMaps>
<rewriteMap name="MapSSL" defaultValue="http://">
<add key="ON" value="https://" />
<add key="OFF" value="http://" />
</rewriteMap>
</rewriteMaps>
</rewrite>

This works fine. However, there's now a requirement to redirect one of the inbound domains (olddomain.com) to a new domain (newdomain.com), so I've added the following rule after the first ('Redirect to https') rule:

<rule name="Old to new domain" enabled="true">
<match url="^olddomain\.com$" />
<action type="Redirect" url="https://www.newdomain.com" redirectType="Permanent" />
</rule>

It doesn't need to maintain any of the old URLs, just any request into olddomain.com (e.g. olddomain.com/whatever) can redirect to the root 'newdomain.com' domain.

Can anyone advise how to correct the new rule since it doesn't seem to do anything?

Many thanks.

The regex you've written may be right (not sure). But when looking at one of the rules I've written to redirect non-www to www, I don't need to escape the period in the domain name. Maybe this works:

<rule name="OldToNewDomain" stopProcessing="true">
  <match url="(.*)" />
  <conditions>
    <add input="{HTTP_HOST}" pattern="^olddomain.com$" />
  </conditions>
  <action type="Redirect" url="http://www.example.com/" redirectType="Permanent" />
</rule>

Source: Web.config redirects with rewrite rules - https, www, and more