Simpson Thacher & Bartlett and Skadden, Arps, Slate, Meagher & Flom have the lead roles in Chinese e-commerce giant Alibaba Group Holding Ltd.’s $1.22 billion investment, with a private equity fund led by Alibaba chairman Jack Ma, in online video company Youku Tudou Inc.

Hangzhou-based Alibaba and Ma’s Yunfeng Capital will pay a 26.3 percent premium for a joint 18.5 percent stake in Nasdaq-listed Youku Tudou, the result of a $1.1 billion merger between Chinese YouTube-like video sites Youku and Tudou in 2012.

The deal is Alibaba’s latest move to expand its online media offerings amid fierce competition with Shenzhen-based Tencent Holdings Ltd., which operates its own QQ Video site. Both companies are vying to build integrated online platforms combining social media functions with a wide variety of other services.

Simpson Thacher Hong Kong partner Kathryn Sudol and Palo Alto partner Katharine Moir are advising Alibaba on the deal, with Fangda Partners as Chinese counsel.* Walkers is serving as Cayman Islands counsel to Alibaba. Simpson Thacher is also acting for Alibaba on its planned U.S. initial public offering, expected to be the largest in the world since Facebook Inc.’s $16 billion listing in 2012. Shearman & Sterling Beijing partner Lee Edwards is advising Yunfeng Capital.*

Skadden Hong Kong partner Julie Gao is representing Youku Tudou, with TransAsia Lawyers advising on Chinese law. Maples and Calder is Cayman Islands counsel to Youku Tudou.*

O’Melveny & Myers New York partner Paul Scrivano and Silicon Valley partner Steven Tonsfeldt are advising 1Verge Holdings Ltd., the largest shareholder in Youku Tudou. An Internet television company, 1Verge is co-owned by Youku Tudou chairman Victor Koo.

Email: azhang@alm.com.

*Updated, 4/29/14, 2:08 p.m.: This story has been updated to include the Simpson Thacher and Skadden partners advising on Alibaba and Youku on the investment, respectively.

*Updated, 4/30/14: This story has been updated to include Simpson Thacher Palo Alto partner Katharine Moir’s role in advising Alibaba. Also, we have included the role of Shearman Beijing partner Lee Edwards as adviser to Yunfeng Capital.