Alkyl Hiyama cross-coupling

Tsuji-Trost allylation reactions offer multiple pathways to tetrahydrofuran synthesis including C-C bond-formation steps. A palladium-catalyzed sequence of allylic alkylation and Hiyama cross-coupling provides a convenient synthesis of 4-(styryl)-lactones (Scheme 67) <2006SL2231>. 

Table 7 Hiyama cross-coupling of primary alkyl bromides and iodides with aryltrimethoxy-silanes...

Table 7 provides examples that illustrate the scope of this room-temperature Hiyama cross-coupling of unactivated primary alkyl bromides and iodides. The method is compatible with functional groups such as esters, cyanides, and ketones. 

Hiyama Cross-couplings. Organosilanes undergo crosscoupling reactions with both primary and secondary alkyl bromides or iodides. Trifluorosilanes are converted to the corresponding products using a nickel/bathophenanthroline catalytic system (eq 7). Moreover, the reaction is compatible with functionalities such as ketones, carbamates, aryl and alkyl chlorides, lactones, acetals, and nitriles. ... 

The palladium-catalyzed reaction of alkenyl-, aryl-, alkynyl- and alkylsiloxanes with aryl, alkyl, and alkenyl halides and triflates in the presence of activators is known as the Hiyama cross-coupling reaction and several reviews have been published. This chapter will present major developments and examples of recent carbon-carbon bond formation methodology and improvements as well as their use in natural products synthesis in the last few years. 

The Hiyama coupling offers a practical alternative when selectivity and/or availability of other reagents are problematic. Hiyama et al. coupled alkyltrifluorosilane 74 with 2-bromofuran 73 to give the corresponding cross-coupled product 75 in moderate yield in the presence of catalytic Pd(Ph3P)4 and 3 equivalents of TBAF [65]. In this case, more than one equivalent of fluoride ion was needed to form a pentacoordinated silicate. On the other hand, alkyltrifluorosilane 74 was prepared by hydrosilylation of the corresponding terminal olefin with trichlorosilane followed by fluorination with C11F2. This method provides a facile protocol for the synthesis of alkyl-substituted aromatic compounds. 

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