In researching this topic, I was unable to pinpoint any specific Islamic leaders who fled to Timbuktu for refuge.  I did discover, however, that there were several rulers of Mali who were Islamic, and who were instrumental in cultivating the prosperity and diversity of Timbuktu and its neighboring city,  Gao.  Through their efforts, Timbuktu became a center of learning and cultural diversity, leading many students and followers of Islam to migrate there to enjoy the security and shelter of a religious culture brimming with learning and knowledge. 

The most famous of these Islamic rulers was Mansa Musa I, who reigned in the 14th century.  "Mansa" is a Mandinka word meaning "king of kings."  Musa I was a devout Islam and a kind, generous man.  During his reign, he founded one of the first universities in the world, the University of Sankore, portions of which still stand today.  Architecture and art fluorished, producing some of the most beautiful books, tapestries, mosques, and cultural halls ever built on earth!  Not only that, merchants came from all over the known world, making Timbuktu a center of trade for years.  Through this means, the Islam religion was adopted by many and spread rapidly out into the world.