Hunter Biden ramped up business activities with European and Chinese tycoons as his father exited the vice presidency four years ago. For him it was a potential path to income; for the tycoons, the Biden family name promised to burnish their reputations.

The dealings got the younger Mr. Biden a discounted stake in a private-equity firm in China and consulting arrangements with a Romanian property magnate and overall allowed him to maintain a globe-trotting lifestyle, according to interviews, documents and communications reviewed by The Wall Street Journal. A Chinese energy tycoon gave Mr. Biden a 2.8-carat diamond, and entities linked to him wired nearly $5 million to Mr. Biden’s law firm, according to an investigation by Senate Republicans…

None of the Journal’s reporting found that Joe Biden was involved in his son’s business activities. The tax investigation doesn’t implicate the president-elect, according to people familiar with the matter…

Some of Hunter Biden’s business deals appeared to go nowhere. Sometimes his contribution mainly consisted of making introductions to important people in business and government, according to people involved and documents.