The Senate last night approved a $14 billion supplemental appropriations bill for the rest of fiscal 1982 after bowing to recession realities in an election year and sanctioning funds to finance extended unemployment benefits for hundreds of thousands of jobless workers.

While not authorizing the extended benefits, it voted overwhelmingly to provide whatever funds are necessary to finance an expected House-Senate compromise on the issue.

The overall spending measure, approved earlier by the House in somewhat different form, now goes to a conference to iron out differences, including whether to approve $355 million in economic aid sought by President Reagan for Caribbean Basin and Central American countries. The Senate approved the aid; the House did not.

While Reagan has not threatened to veto the money bill, a veto is considered possible in light of the fact that the bill, which is required mainly to pay for federal workers' pay raises, gives the president less for defense and more for domestic programs than he wants. More than $600 million for jobs for the elderly, student aid and programs for the handicapped is at issue, according to Senate sources.

Before the Senate approved the measure by voice vote, it added a few election-year goodies for some especially persistent members, including an amendment pushed by Sen. Harrison H. Schmitt (R-N.M.) to require that proceeds from the sale of excess strategic materials be used to purchase copper. Unemployment is high in copper-smelting regions of New Mexico; Schmitt is seeking reelection this fall.

But the Senate also struck a blow for economy in approving an amendment from Sens. James Abdnor (R-S.D.) and Dennis DeConcini (D-Ariz.) to prohibit the Internal Revenue Service from spending $85,000 to remodel executive offices at the IRS.

The vote for the unemployment benefits money, also proposed by Schmitt, was 96 to 3, with Sens. Harry F. Byrd Jr. (Ind.-Va.), Jesse Helms (R-N.C.) and Gordon J. Humphrey (R-N.H.) voting against it.

The Senate voted last week to push, in a House-Senate conference on tax increases and spending cuts, for a liberalization of the jobless benefits program, including protection of states that are losing 13 weeks of extended benefits on top of the regular 26 weeks of benefits, and the possibility of supplemental benefits for another 13 weeks.

The conference remained stymied yesterday, however, over a dispute involving House efforts to restore some of the welfare cuts that Congress made last year at President Reagan's behest.

The conference, despite pressures to finish quickly, did not convene formally but held behind-the-scenes discussions yesterday. The conferees are to meet today.

The extended unemployment benefits are seen as a possible "sweetener" to help get support, especially among Democrats, for the tax bill, which would raise nearly $100 billion in revenues to help reduce deficits over the next three years.

Senate Democrats reportedly were considering proposals to authorize the extended benefits as part of the supplemental money bill yesterday but did not make the proposal. As adopted, the proposal from Schmitt simply provided for appropriation of "such sums as may be necessary" to implement whatever legislation is finally agreed upon.

Meanwhile, House and Senate conferees on a separate set of spending cuts, including a disputed proposal to limit annual inflation adjustments for federal workers' pensions to 4 percent, began work on a compromise in hopes of finishing by the end of the week.

Backers of the tax measure are also hoping for final action on the spending cuts by the middle of next week as an added inducement for passage of the tax increase. Many Republicans are insisting that spending cuts be nailed down before they will consider voting for a tax increase.