Cross-coupling, platinum-catalyzed

PLATINUM CATALYZED HYDROSILYLATION AND PALLADIUM CATALYZED CROSS-COUPLING ONE-POT HYDROARYLATION OF 1-HEPTYNE TO (E)-l-(l-HEPTENYL)-4-... 

A separate, quite thorough study of terminal alkyne hydrosilylation with platinum arrived at a similar set of conditions.39 This work utilized a one-pot hydrosilylation with the preformed platinum(O) complex (>Bu3P)Pt[(CH2=CH)Me2Si]20 ([(CH2=CH)Me2Si]20 = DVDS) and subsequent palladium-catalyzed coupling reaction to demonstrate that the platinum catalyst is compatible with cross-coupling conditions, providing a convenient hydrocarbation of terminal alkynes (Table 2). 

Denmark pursued intramolecular alkyne hydrosilylation in the context of generating stereodefined vinylsilanes for cross-coupling chemistry (Scheme 21). Cyclic siloxanes from platinum-catalyzed hydrosilylation were used in a coupling reaction, affording good yields with a variety of aryl iodides.84 The three steps are mutually compatible and can be carried out as a one-pot hydro-arylation of propargylic alcohols. The isomeric trans-exo-dig addition was also achieved. Despite the fact that many catalysts for terminal alkyne hydrosilylation react poorly with internal alkynes, the group found that ruthenium(n) chloride arene complexes—which provide complete selectivity for trans-... 

Both amido and pinacol derivatives of B-Si compounds 125 and 126 added to terminal and internal alkynes in the presence of a palladium244-246 or platinum(O) catalyst247 by a mechanism involving an oxidative addition-insertion process (Equation (39)).248 On the other hand, phosphine-free nickel(O) catalyst resulted in the dimerization of alkynes giving a Z,Z-isomer of l-silyl-4-borylbutadiene derivatives.249 Since the palladium-catalyzed cross-coupling at the C-B bond is faster than the G-Si bond of 137, a silylboration-cross-coupling sequence provided a method for the synthesis of 1-alkenylsilanes.246... 

Taking advantage of the slow hydrogenation of carbon-carbon double bonds at room temperature in the presence of platinum dioxide, it was possible to perform the ruthenium-catalyzed cross coupling reaction of electron-deficient olefins such as conjugated enones and acrylic derivatives with allyl silanes in the presence of Pt(>2 under hydrogen (Scheme 46) [99]. Prolonged... 

Palladium and platinum form numerous alkyl complexes of the types M(R)(X)L2 and MR2L2, usually stabilized by phosphine ligands. The palladium compounds are prone to reductive elimination this is important in palladium catalyzed cross-coupling reactions (Section 21-14) ... 

Platinum-catalyzed cross-coupling with Grignard compds. ArC = CAr ... 

A mixture of p-fluorophenylmagnesium bromide, /7-methoxyphenylethenyl bromide, and 2 mol% Pt-rj -alkene complex (prepared by reacting dichloro[l,T-bis(diphenyl-phosphino)ferrocene]platinum(II) with /7-methoxyphenylethenyl bromide in THF at room temp.) in THF refluxed for 2 days - product. Y 95%. This is the first report of efficient Pt-catalyzed cross-coupling with Grignard reagents. F.e.s. J.M. Brown et al., J. Chem. Soc. Chem. Commun. 1989, 458-60. 

Several independent protocols using a combination of transition metal-catalyzed stereoselective hydrosilylation, such as palladium-catalyzed crosscoupling sequence leading to stereodefined r-conjugated alkene derivatives, have been successfully developed in the last decade (4). Alkenylsilanes or siloxanes, prepared via platinum or rhodium complex-catalyzed intermolecular hydrosilylation of terminal alkynes have been highly stereospecifically cross-coupled with aryl and alkenyl halides to give unsymmetrical stilbenes, alkenylbenzenes, and conjugated dienes (Scheme 24) (4). 

Kuniyasu H, Yamashita F, Hirai T, Ye J, Fujiwara S, Kambe N. Platinum-catalyzed reaction of alkynes with Arl (Ar = aryl and thienyl) and Ar SM (M = Na, K, and Sn(n-Bu)3 three vs two-component cross-coupling reaction. Organome-tallics 2006 25 566-570. 

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