Barcelona have reportedly reached an agreement to sign Borussia Dortmund winger Karim Adeyemi in a deal that could become one of the most unusual transfers in the ongoing transfer window.While the Catalan giants are expected to pay an initial €22 million, with a further €9 million in performance-related bonuses, Dortmund have negotiated a staggering 35 per cent sell-on clause for any future transfer involving the Germany international!Unlikely forward coming to BarcelonaSuch an arrangement is highly uncommon, particularly for a player entering the final year of his contract. Rather than insisting on their original €40 million valuation, Dortmund are said to have accepted a lower upfront fee in exchange for the opportunity to profit significantly if Adeyemi earns another big-money move later in his career.According to reports, Hansi Flick played a decisive role in convincing Barcelona to pursue the 24-year-old, viewing his pace and versatility as ideal additions to the club's attack. Adeyemi is also believed to have rejected offers from the Premier League in favour of a move to Camp Nou and is expected to sign a five-year contract.The transfer would further strengthen Barcelona's wide attacking options following the arrival of Anthony Gordon earlier this summer, giving Flick another explosive weapon ahead of the new campaign.##NAJAVA_MECA_9842049##Barcelona's work in the transfer market may not stop there. Spanish reports claim the club are still preparing an ambitious move for Atletico Madrid striker Julian Alvarez as they continue planning for life after Robert Lewandowski, although any deal would require a major financial commitment.