Untangling large nested if else code structures in C#

I have inherited a large nested if else structure, I am trying to separate the leaves of the if else tree into separate if statements only e.g. :

if ( c1 )
  { dc1 }
else if ( c2 )
          { dc2 }
     else {dc3}

should become something like :

if (c1) {dc1;}

if ((!c1) & (c2)) {dc2;}

if ((!c1) & (!c2)) {dc3;}

This is much simpler than the unholy structure I am trying to untangle.

Side question : it easy to see that there is no condition that takes into account the case

if ((c1) & (c2)) 

is there a tool or simpler way of linearising the if else structures and seeing all the conditions that have not been included.

I hope my example is correct.