D.C. Court of Appeals Chief Judge Theodore R. Newman Jr. has privately told friends that he has made a firm decision not to seek reappointment next year to another four-year term as head of the city's highest court and has been actively seeking a job in the private sector.

Sources close to Newman, 48, say he quietly established an informal committee of prominent friends late last year to assist him in finding a job.

That committee, composed of four prominent Washington lawyers--John Pickering, Charles Horsky, William Coleman and Vincent Cohen--has been "putting out the word," one source said, that Newman would be available. No firm offers have been presented to Newman, according to reliable sources.

Sources close to Newman say he established the informal committee in order to avoid having to talk to firms himself and run into ethical conflict-of-interest problems should lawyers from those firms appear before him. One member of the group described it as a "blind trust" committee.

Another committee member said the search for an acceptable offer was difficult because, as a sitting judge, Newman not only has no clients to bring to a firm but also has been barred from even having client contacts while on the bench.

It is fairly uncommon for judges at Newman's level to leave the bench. The committee, said one member, is a slightly more formal version of the usual way in which government lawyers often announce their intention to seek private employment.

Newman, first appointed to the court by then-president Gerald Ford in 1976, was named chief judge by the city's judicial nominating commission. Appellate judges serve 15-year terms--Newman's expires in 1991--and the position of chief judge, filled by the nominating commission, is a four-year appointment. Newman's term as chief judge expires in October 1984.

The tenure of the liberal and often combative Newman has been marked by bitter personality clashes with other judges on the court.

Those clashes surfaced publicly three years ago when four conservative judges--Frank Q. Nebeker, Stanley S. Harris, George R. Gallagher and John W. Kern III--opposed Newman's reappointment. Sources familiar with the appointment process said Newman's reappointment came on a close vote of the judicial nominating commission, and said they doubted he could now get enough votes for another term.

Two of the four judges who opposed Newman, Harris and Gallagher, have since left the court. Sources familiar with the situation said the bickering on the court has not stopped, but that a moderate middle group, consisting of judges James A. Belson, William C. Pryor and occasionally John A. Terry, has developed.

Those sources expect that D.C. Corporation Counsel Judith W. Rogers, nominated yesterday by President Reagan to a seat on the court, will avoid the personality clashes and align herself with the more moderate members of the court.

Current leading contenders to replace Newman are Belson and Judge John M. Ferren, a liberal on the court. Rogers is considered by some as a possible candidate, though she will only have been on the court one year when Newman's term expires.