Over recent decades, transition-metal-catalyzed bond-forming reactions using the cross-coupling strategy have become extremely powerful tools for the synthesis of an array of small organic molecules and macromolecules. [1,2] More recently, transition-metal-catalyzed carbon-carbon bond-forming reactions by C(sp 3 ) ร H bond activation have emerged as new efficient tools for synthetic organic chemistry. [3,4] Inspired by recent elegant examples of tandem/"domino" reactions, [5][6][7] we reasoned that these two types of powerful transitionmetal-catalyzed reactions could be transformed into even more powerful tools if they could be arranged to occur in a tandem or "domino" fashion. We were particularly attracted by the possibility of having ring-forming tandem or "domino" reactions that combine transition-metal-catalyzed cross-couplings and an C(sp 3 )รH bond-activation strategy, as such reactions could not only concomitantly generate multiple bonds with a rapid increase in molecular complexity but also allow us to access ring systems that are difficult to access by other methods. Herein, we report a new type of such annulative tandem reaction-Pd 0 /tBu 3 P-catalyzed tandem reactions of 1,2-dihalobenzenes with hindered Grignard reagents-which provides efficient access to substituted fluorenes. [8,9] Our mechanistic consideration of the Pd-catalyzed tandem reaction of 1,2-dihalobenzenes is shown in Scheme 1. We envisioned that a Pd 0 -catalyzed reaction of a 1,2-dihalobenzene with an organometallic reagent would generate the initial cross-coupling product I and recognized that its subsequent oxidative-addition product, the Pd II complex II, could 1) couple with another equivalent of an organometallic reagent to yield the direct cross-coupling product and/or 2) undergo intramolecular C(sp 3 ) ร H bond activation followed by cyclization (Scheme 1). As the crosscoupling of aryl halides with organometallic reagents is well [*] C.