Cross coupling reactions halides

Cross-coupling reactions of aromatic or vinylic halides and olefins catalyzed by palladium. 

They have also developed a route to 2-allenylindole derivatives (98T13929). When prop-2-ynyl carbonates (76) are reacted with 73 in the presence of palladium catalyst, a cross-coupling reaction occurs to give 77a (46%) and 77b (45%). Under a pressurized carbon monoxide atmosphere (10 atm), the palladium-catalyzed reaction of 73 with 78 provides 79a (60%) and 79b (60%) (2000H2201). In a similar reaction, when the substrate is changed to aryl halides (80), 2-aryl-1-methoxyindoles such as 81a (70%) and 81b (60%) are prepared (97H2309). 

Carbon-carbon bond formation reactions and the CH activation of methane are another example where NHC complexes have been used successfully in catalytic applications. Palladium-catalysed reactions include Heck-type reactions, especially the Mizoroki-Heck reaction itself [171-175], and various cross-coupling reactions [176-182]. They have also been found useful for related reactions like the Sonogashira coupling [183-185] or the Buchwald-Hartwig amination [186-189]. The reactions are similar concerning the first step of the catalytic cycle, the oxidative addition of aryl halides to palladium(O) species. This is facilitated by electron-donating substituents and therefore the development of highly active catalysts has focussed on NHC complexes. 

Our group has recently developed an alternative method for alkyl-(hetero)aryl- as well as aryl-heteroaryl cross coupling reactions catalyzed by iron salts.3 4 This methodology was inspired by early reports of Kochi et al.5>6 on iron-catalyzed cross coupling of vinyl halides and is distinguished by several notable advantages. 

Chromans have been obtained by the Pd-catalysed intramolecular cross coupling reaction involving aryl halides containing an ortto-hydroxyalkyl substituent <96JA10333>. 

Palladium catalyzed cross-coupling reactions of arylhalides or halide equivalents with various nucleophiles have been shown to be highly effective and practical... 

Palladium And/Or Copper-Mediated Cross-Coupling Reactions Between 1-Alkynes And Vinyl, Aryl, 1-Alkynyl, 1,2-Propadienyl, Propargyl And Allylic Halides Or Related Compounds. A Review, Rossi. R. Carpita, A. Beilina, F. Org. Prep. Proceed. Int., 1995, 27, 129... 

Scheme 29 Iron-catalyzed cross coupling reaction of aryl Grignard reagents with alkyl halides...

As complex 67 outperforms the Fe(0)-ate complexes in rate and yield, shown in the reaction of cyclooctenyl bromide with PhMgBr (full conversion complex 67 <20 min, 81% yield, 38 18 h, 39% yield), it was shown that both Fe(0)-ate and Fe (—2)-ate complexes should be intermediates in cross-coupling reactions, but the major contribution should be made by the route emanating from Fe(—2)-com-plexes. The superiority of Fe(—2)-ate complexes was also shown in the stoichiometric insertion of 67 into allylic halides, which proceeded much faster (<5 min) than with any higher valent iron complex (hours or days). 

Erase S, de Meijere A(2004) Cross-coupling of organic halides withalkenes The Heck reaction. In de Meijere A, Diederich F (eds) Metal-catalyzed cross-coupling reactions, 2nd edn. Wiley-VCH, Weinheim... 

The generated palladium chlorides possessing phosphinous acid ligands were found to be remarkably active and efficient catalysts in the presence of bases for a variety of cross-coupling reactions of aryl halides with aiylboronic... 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

The cross-coupling reactions of benzylic halides and acyl halides produced the expected ketones in good to high yields(39,47). The present method can supplement the corresponding Grignard reaction, which does not work well since benzylmagnesium halides undergo dimerization readily. 

---