Alex's Attempt  

It's still pretty good for White, sacrificing one more stone (White 1 is now disposable too).

Alex's Attempt (ii)  

B 1 is big. If White plays there she threatens a.

Heavy  

Charles Matthews After Black 4, I wouldn't want to be White here. The group is too heavy.

Proposed alternate solution

It's not in the solution, but doesn't this also prevent the Black stone on the right from joining?

...another continued variation...  

White has sente this way?

is bad?  

I think if White tries in response to , there is the feeling that White hasn't claimed anything of substance. Those four White stones are weak.

Liberties are important  

Herman: After , still has 4 liberties. With the driving tesuji, white can force that stone's liberties down to 3 in sente.

After , white must defend, so:

Under attack  

Herman: You proposed , but since the marked white stone is not important, capturing that is an endgame move for black. So instead, black could attack with and . After the driving tesuji, is not sente.

Taking that liberty  

Herman: An alternative here is for white to take that black liberty with . Now black has no sente moves here. Note, however, that this diagram looks very much like the diagram after the driving tesuji, but in that diagram white gets stones at all the points marked a, in exchange for the marked stone , which is captured by black. That exchange definitely favors white, who gets a much bigger and stronger wall in exchange for a few points (which black can get in this diagram as well, should he so choose.