Lead-carbon bonds silver salts

Activation of carbon—hydrogen bonds in benzyl phenyl sulfoxides catalysed by palladium may lead to dibenzothiophene derivatives (39). lodoarenes and silver salts are required as additives, and product formation requires several consecutive catalytic cycles. The copper-catalysed conversion of bisaryloxime ethers to 2-arylbenzoxazoles is likely to involve complexation of the catalyst at... 

The relative ease of the cyclization step from A to C may also be linked to the nucleophilic or coordinative ability of the heteroatom bound to the metal. The reaction of 7 with diphenylacetylene (Ph2C2) leads to the seven-membered derivatives 68 and 69 after prior isolation of the monoinsertion product 24, treatment with a silver salt, followed by the usual thermolytic conditions. This is another rare example of an intramolecular formation of a C-S bond within the coordination sphere of a transition metal and a novel, albeit limited to one alkyne, route to the rare family of dibenzo[bd] thiepins. With the closely related 8, which differs from 7 only by the tertiary amine unit in the metallacyclic framework instead of a thioether function, a carbocyclic product 71 is obtained (see under carbocycle reactions, next section). The formation of the seven-membered S-heterocycles is attributed to the good coordinative ability of the thioether group in 7. The S-atom remains close to the vinylic carbon function before the cyclization. With the poorly coordinating, readily displaced amine function in 8, the N-atom is detached from the metal and ultimately affords a spirocyclic product (see Scheme 18). 

Most of the above oxidative alkenylations take place with 2-5 mol% of a Ru (11) species and excess of silver salt, usually 20 mol%, and 1 equiv of Cu(ll) unless the reaction can be performed in air. As [RuCl2(p-cymene)]2 leads to partial formation of Ru(OAc)2(p-cymene) with Cu(0Ac)2.H20 [160], AgSbFg by abstracting the chlorides is expected to increase the formation of Ru (OAc)2(p-cymene). The Ru-OAc bond of the latter dissociates easily [49, 91] to allow the coordination of the heterocycle Directing Group (D=G) to the Ru (II) centre (Scheme 16). The interaction of the Ru(II) site with the ortho carbon atom (A) is expected to favour the deprotonation of its C-H bond by the external... 

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