Transition-metal-catalyzed cross-coupling reactions between organic halides and organometallic reagents is a powerful tool for constructing carbon skeletons.[1] Significant advances have been achieved in this field over the last decade that have enabled cross-coupling reactions to be effected between alkyl groups by using either a nickel or palladium catalyst.[2] We have contributed to this progress by developing a unique catalytic system that proceeds efficiently under mild conditions by using 1,3-butadiene as an additive in the absence of phosphane ligands, where bis-p-allylnickel or -palladium intermediates (1) are proposed to be involved [Eq. (1)]. [3] This system facilitates the cross-coupling of a wide variety of alkyl tosylates and halides, such as fluorides, chlorides, and bromides, with Grignard reagents. However, a drawback of this methodology is the range of functional groups that are tolerant to this system because of the high reactivity of the Grignard reagents. Herein, we reveal a solution to this problem by employing 1,3,8,10-tetraenes (2) that serve as extremely efficient ligands to promote the nickel-catalyzed cross-coupling reaction of alkyl halides with organozinc reagents [4][5][6] in a THF/N-methylpyrrolidone (NMP) mixed solvent containing magnesium bromide. It was also found that these tetraenes (2) were effective also for the nickel-catalyzed cross-coupling of alkyl fluorides with Grignard reagents.First we examined a cross-coupling reaction of alkyl halides with organozinc reagents that used 1,3-butadiene as the additive. For example, n-decyl bromide (1 mmol), diethylzinc (2 equivalents, 1m in hexane), NiCl 2 (0.03 equiv), and 1,3-butadiene (1 equivalent) were added sequentially to a solution of THF (8 mL) and NMP (4 mL) at À78 8C and the mixture stirred at 25 8C for 48 hours. However, this reaction gave only a trace amount of the cross-coupling product, ndodecane (< 1 %), as shown in Table 1 (entry 1). Addition of magnesium bromide increased the yield of n-dodecane to 45 %, but side reactions (reduction and HBr elimination) could not be suppressed (entry 2). Only a trace amount of dodecane was obtained without 1,3-butadiene even in the presence of magnesium bromide (entries 3 and 4). The salts Bu 4 NBr, Bu 4 NI, [5] and LiBr were also shown to be not effective as additives (entries 5-7). The yield of dodecane was increased up to 73 % by adding four equivalents of 1,3-butadiene; however, formation of by-products, n-decane and decenes, could not completely be suppressed (entries 8 and 9). Under similar conditions, [Ni(acac) 2 ] (acac = acetylacetanoate) afforded a slightly better yield of the product (entry 10), while nickel catalysts bearing phosphane ligands were less efficient (entries 11 and 12). PdCl 2 did not show a high catalytic activity (entry 13). The coupling products were obtained in yields of only 37 and 7 %, respectively (entries 14 and 15), when isoprene and p-fluorostyrene [5] were employed as additives under the same conditions as entry 10.It is noteworthy that this cross-c...