* Arsenal frustrated in 0-0 draw with Middlesbrough
* Boro's Gaston Ramirez struck post with a free kick
* Ramirez wasted two other great chances
* Arsenal's Alexis Sanchez was denied by Victor Valdes save
* Mesut Ozil had late goal disallowed
* Arsenal at Sunderland next, Boro host Bournemouth (Adds details, quotes)
Oct 22 (Reuters) - Arsenal moved top of the Premier League for the first time this season but were left frustrated by Middlesbrough in a 0-0 draw - the first time they had failed to score at home since defeat by Barcelona in February.
It could have been worse too for Arsenal on manager Arsene Wenger's 67th birthday as it was the visitors who carved out the better chances, especially in the first half when they were denied by Petr Cech and the woodwork.
Arsenal did have a late effort disallowed as they moved to 20 points from nine matches, level with Liverpool who beat West Bromwich Albion and one above Manchester City, who play Southampton on Sunday, and Tottenham Hotspur.
"They had chances but our goalkeeper saved us today. Cech had a good performance in decisive phases," Wenger said.
"We are not happy but at least we didn't lose it. We were a little jaded. We played Wednesday and you could see that some of the legs and heads were not sharp."
Cech was rested for the midweek Champions League tie and was razor sharp on his return.
"When they had their chances and they didn't take them I thought that we were going to punish them for that," he told the club's website. "Overall, they had plenty of chances as well so I think we have to say maybe a draw is a fair result."
Arsenal put six past Bulgarian champions Ludogorets in midweek and not surprisingly began in confident fashion, dominating the opening 20 minutes as they chased a seventh consecutive Premier League win.
When the breakthrough failed to arrive, however, it was Middlesbrough who began to threaten.
Adama Traore broke clear alone midway through the half but Cech saved his shot with his outstretched legs and then stopped Alvaro Negredo's scuffed follow-up effort.
The hosts had another let-off when Gaston Ramirez's curling free kick thumped against the post and shortly afterwards Ramirez headed a great chance straight at Cech.
Arsenal, unbeaten since losing the first game of the season, were better after the break and pressed hard but Boro defended tenaciously to restrict their chances.
Boro keeper Victor Valdes had some anxious moments but made one superb save to keep out former Barcelona team mate Alexis Sanchez's dipping effort.
Mesut Ozil had a late goal rightly disallowed for offside but defeat would have been hard on Boro who remain just above the bottom three after seven league matches without a win. (Reporting by Martyn Herman, editing by Ed Osmond and Pritha Sarkar)