Two months after the U.S. imposed sanctions on Russian construction billionaires Arkady and Boris Rotenberg in March 2014, the brothers sent their art adviser on a shopping spree, according to a Senate investigation report released Wednesday. At a Sotheby’s auction that month in New York, the Rotenbergs, who are lifelong friends of Russian President Vladimir Putin, paid $6.8 million for 10 works of art, including a cubist still life by Georges Braque and a swirling tableau by Marc Chagall, the report said.
Days later, the…