Sugar Ray Leonard, the star who was born on the television screen at the 1976 Olympics, marked the formal announcement yesterday of his March 31 title defense against Englishman Dave (Boy) Green at Capital Centre by asserting that some boxing promoters and managers have not caught up to the financial realities of the 1980s.

"I want $5 million to fight (Roberto) Duran," Leonard said.

That explained why his management recently told promoter Don King that his offer of $2.5 million to Leonard to fight Duran was unacceptable and why King told Leonard's attorney his proposition was unacceptable, because there would not be enough profit in it for the promoter.

Attorney Mike Trainer, who handles Leonard's financial affairs, had tried to negotiate directly with Duran's manager. When an impasse was reached, Duran signed a contract to have King arrange a bout with Leonard.

When King and Trainer stalemated, Trainer entered into a contract with Bob Arum of Top Rank Inc., the New York City promotional firm, for one bout, Leonard against Duran, in May or June. Arum offered Duran $1 million if Duran would accept by Feb. 15.

Arums said yesterday that Leonard will be paid his biggest purse ever for defending his title against Green, "even if nobody attends the live bout" at Capital Centre. That, of course, means Leonard will receive from television more than the $1 million he was paid when he took the championship form Wilfred Benitez.

Arum is copromoting the Leonard-Green show with Capital Centre and said that if it "does well," despite no area television blackout, Leonard will take home an aggregate of about $1.4 million.

Tickets will cost from $10 to $100 and matchmaker Eddie Hrica predicted the fight will draw at least $15,000. Leonard attracted a Maryland record 19,000 persons to the Centre for his Jan. 11, 1979, bout with Johnny Gant.

Arum said of the shift of the Leonard-Green bout from Las Vegas to Capital Centre: "Boxing, to flourish, has to spread bouts around the country. If there are too many bouts in Las Vegas, people will begin to associate boxing, television and gambling."

Green has a 33-2 record. Leonard watched on tape a round of Green's loss to former WBC welterwieght champ Carlos Palomino and said, "If he (Green) cooperates (mixes it up) our bout will last three or four rounds."

Green made no prediction. He praised Leonard as a "technician," and described himself as a "box fighter."