* Fed Chair Yellen to speak at Jackson Hole on Friday
* Dollar rises for second day on interest rate hike bets
* Medivation jumps on $14 bln Pfizer deal
* Futures down: Dow 34 pts, S&P 3.25 pts, Nasdaq 6.25 pts (Adds details, comments, updates prices)
By Yashaswini Swamynathan
Aug 22 (Reuters) - Wall Street looked set for a lower open on Monday as oil prices dropped the most in four weeks and dollar strengthened on bets of an interest rate hike in the coming months.
With the earnings season coming to an end, investor focus will shift to Federal Reserve Chair Janet Yellen's speech on Friday at the annual central bankers' meeting in Jackson Hole, Wyoming.
"The markets will start to get a little bit nervous about what's going to be said, what kind of indications will be given about a September hike," said Robert Pavlik, chief market strategist at Boston Private Wealth in New York.
The case for an imminent rate hike was strengthened by Fed Vice Chairman Stanley Fischer's comments that the U.S. economy was close to hitting job and inflation targets.
New York Fed president and permanent voting member William Dudley said last week that a hike as soon as next month was possible.
The dollar index rose for the second day, after five straight sessions of losses, on prospects of a rate hike in the coming months.
Traders have priced in a 12 percent chance of a rate hike for September and a 39.1 percent chance for December, according to the CME Group's FedWatch tool.
Oil prices fell nearly 3 percent on Monday as China ramped up exports of refined products, U.S. producers added rigs for an eighth consecutive week, and prospects emerged for increased exports from Iraq and Nigeria.
Wall Street closed lower on Friday, with the major indexes barely making any gains for the week, as investors weighed prospects of a rate hike.
Dow e-minis were down 34 points, or 0.18 percent, at 8:31 a.m. ET (1231 GMT) on Monday, with 19,703 contracts changing hands.
S&P 500 e-minis were down 3.25 points, or 0.15 percent, with 180,941 contracts traded.
Nasdaq 100 e-minis were down 6.25 points, or 0.13 percent, on volume of 25,152 contracts.
Medivation shares jumped 19.8 percent to $80.43 premarket after agreeing to be bought by Pfizer for $14 billion. Pfizer's shares were marginally lower at $34.75.
Syngenta's U.S.-listed shares jumped 11.3 percent after a U.S. national security panel cleared ChemChina's $43 billion takeover of the Swiss pesticides and seeds group.
Valeant's U.S.-listed shares rose 3.4 percent to $29.73 after the Canadian drugmaker named a new chief financial officer.
Chipmaker Intersil jumped 28 percent $20 after a source told Reuters that Japan's Renesas was in the final stages of negotiations to acquire the company for about $2.99 billion. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Don Sebastian)