Here's a preview of five earnings reports to watch for on Tuesday before the bell: Despite an expected dip in profit, analysts are generally optimistic about Pfizer Inc. (NYSE: PFE) as it prepares to reports its first quarter earnings on Tuesday before the bell, according to estimates from Zachs. Although analysts are projecting Pfizer to come in with earnings of 55 cents per share, the company has seen steady earnings for the last eight quarters.Also on Tuesday, Wall Street is expecting higher profit for NYSE Euronext (NYSE: NYX), with the Zachs consensus estimate is calling for profit of 56 cents a share, a rise from 47 cents per share a year ago.Wall Street is optimistic about Avon Products, Inc. (NYSE: AVP), with a projected profit of 14 cents a share, a rise from 10 cents per share a year ago, however Zachs analysts expect revenue to fall 2.5 percent year-over-year for the quarter.The McGraw-Hill Companies Inc. (NYSE: MHP) is expected to report first-quarter earnings of 73 cents per share on revenue of $1.17 billion, up from a profit of 51 cents in the year-ago period, according to Zachs. Although expectations have fallen over the past month for Valero Energy Corporation (NYSE: VLO), Zachs analysts' estimates are up 225.8% from the year-ago quarter when the company reported earnings of 31 cents per share. Analysts now forecast the company to reports earnings of just over a dollar per share.