Coupling agents alkenes

The preparation of rigid alicyclic molecules bearing effector groups from alkene blocks using s-tetrazines and 1,3,4-triazines as stereoselective coupling agents [67]... 

Wood flour from maple, 120 mesh, vacuum dried. The coupling agent was maleated polyethylene containing 1% (w/w) grafted maleic anhydride (Epolene G-2608, Eastman Chemicals). The lubricant was alkene bis fatty amid (Glycolube WP-2002, Lonza Inc.) [4]. 

Dialkyl ketones/ The reductive coupling of alkenes and carbon monoxide at room temperature is promoted by CoCl2-Ph(Et)2N BH3 (7 examples, 50-70%). The generation of ClBHj as hydroborating agent for the alkenes is implicated, and the subsequent carbonylation is assisted by cobalt carbonyl species formed in situ. 

Vinylsilanes are important alkene derivatives that have been widely used as synthetic intermediates, monomers for copolymer plastics, and coupling agents for hybrid silicon materials (1). Transition-metal-catalyzed hydrosilylation and bis-silylation of alkynes represent the most straightforward and atom-economic routes to vinylsilanes (2). The original reports on palladium-catalyzed bis-silylation of alkynes with disilanes were published by Kumada and Sakurai (3). 

The same transition metal systems which activate alkenes, alkadienes and alkynes to undergo nucleophilic attack by heteroatom nucleophiles also promote the reaction of carbon nucleophiles with these unsaturated compounds, and most of the chemistry in Scheme 1 in Section 3.1.2 of this volume is also applicable in these systems. However two additional problems which seriously limit the synthetic utility of these reactions are encountered with carbon nucleophiles. Most carbanions arc strong reducing agents, while many electrophilic metals such as palladium(II) are readily reduced. Thus, oxidative coupling of the carbanion, with concomitant reduction of the metal, is often encountered when carbon nucleophiles arc studied. In addition, catalytic cycles invariably require reoxidation of the metal used to activate the alkene [usually palladium(II)]. Since carbanions are more readily oxidized than are the metals used, catalysis of alkene, diene and alkyne alkylation has rarely been achieved. Thus, virtually all of the reactions discussed below require stoichiometric quantities of the transition metal, and are practical only when the ease of the transformation or the value of the product overcomes the inherent cost of using large amounts of often expensive transition metals. 

Finally, in 2006, Ellman reported a single example of a sulfinimine-alkene coupling mediated by Sml2 in their work on the total synthesis of the anticancer agent, tubulysin D. It was found that the coupling of enantiomerically pure sulfinimine 67 with methyl methacrylate was effectively promoted by the... 

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