The proposed extension at looks well placed between the White wall and the White corner, but unfortunately the White wall has a glaring weakness. I would instead play to complete the wall, extending its influence into the center, trusting that the gain in thickness will be worth a full move over time.
This does permit Black to reduce or invade below fairly easily, but then White will have something to attack and should be able to get compensation elsewhere, probably by invading the left side. A few possible sequences:
- Click Here To Show Diagram Code
[go]$$Bc B reduces with shoulder hit
$$ --------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O O . O . . . . . O O X . . . |
$$ | . . . X . X O . . , . . O X . X . . . |
$$ | . . . . . X . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . X . . . . . , . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O O . . |
$$ | . . . . . . . . . . . . . X O X O O . |
$$ | . . . . . . . . . . . . O O X X X O . |
$$ | . . X . 4 . . . . . . . @ X . . X X . |
$$ | . . . . . . 3 . . . . . . O X O O X . |
$$ | . . . O . 2 1 . . . . . . . O , O X . |
$$ | . . . . . O . . . . . . . . O O X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ --------------------------------------[/go]
- Click Here To Show Diagram Code
[go]$$Bc B invades directly
$$ --------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O O . O . . . . . O O X . . . |
$$ | . . . X . X O . . , . . O X . X . . . |
$$ | . . . . . X . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . X . . . . . , . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O O . . |
$$ | . . . . . . . . . . . . . X O X O O . |
$$ | . . . . . . . . . . . . O O X X X O . |
$$ | . . X . . . 4 . . . . . @ X . . X X . |
$$ | . . . . . . . . 3 . . . . O X O O X . |
$$ | . . . O . . . . . 1 . . . . O , O X . |
$$ | . . . . . O . 2 . . . . . . O O X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ --------------------------------------[/go]
The alternative looks worse to me. If White extends from the wall, it looks like Black can activate the cutting stone immediately. If White protects his territory passively, Black gets center strength, the White group above starts looking weak, and the White territory below is not huge. One possible sequence:
- Click Here To Show Diagram Code
[go]$$Bc B exploits the weakness in the wall
$$ --------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O O . O . . . . . O O X . . . |
$$ | . . . X . X O . . , . . O X . X . . . |
$$ | . . . . . X . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . X . . . . . , . . . . O X X . . |
$$ | . . . . . . . . . . . . . . O O O . . |
$$ | . . . . . . . . . . . 5 . X O X O O . |
$$ | . . . . . . . . . . . . O O X X X O . |
$$ | . . X . . . . . . . . 3 1 X 2 . X X . |
$$ | . . . . . . . . . . . . . O . O O X . |
$$ | . . . O . . . . . @ . 4 . . O , O X . |
$$ | . . . . . O . . . . . . . . O O X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ --------------------------------------[/go]
If White attempts to capture the Black cutting stone, a difficult fight erupts, and it is not clear who wins. But even if Black decides this fight is not immediately advisable, the aji is severe -- almost any probe around the bottom will threaten to activate the cut. One possible sequence:
- Click Here To Show Diagram Code
[go]$$Bc B cuts, W fights back
$$ --------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O O . O . . . . . O O X . . . |
$$ | . . . X . X O . . , . . O X . X . . . |
$$ | . . . . . X . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . X . . . . . , . . . . O X X . . |
$$ | . . . . . . . . . . . . 8 . O O O . . |
$$ | . . . . . . . . . . . 7 6 X O X O O . |
$$ | . . . . . . . . . . . 5 O O X X X O . |
$$ | . . X . . . . . . . . 2 1 X 4 . X X . |
$$ | . . . . . . . . . . . . 3 O X O O X . |
$$ | . . . O . . . . . @ . . . . O , O X . |
$$ | . . . . . O . . . . . . . . O O X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ --------------------------------------[/go]
- Click Here To Show Diagram Code
[go]$$Bc B cuts, W fights back, B sacrifices
$$ --------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O O . O . . . . . O O X . . . |
$$ | . . . X . X O . . , . . O X . X . . . |
$$ | . . . . . X . . . . . . . X . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . X . . . . . , . . . . O X X . . |
$$ | . . . . . . . . . . . . O . O O O . . |
$$ | . . . . . . . . . . . X O X O X O O . |
$$ | . . . . . . . . . . . X O O X X X O . |
$$ | . . X . . . . . . . 1 O X X O . X X . |
$$ | . . . . . . . . . . 3 2 X O . O O X . |
$$ | . . . O . . . . . @ 5 4 . . O , O X . |
$$ | . . . . . O . . . . . . . . O O X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ --------------------------------------[/go]