Miscellaneous Reactions of Aryl Halides

13 Account, T. Imamoto, T. Oshiki, T. Onozawa, M. Matsuo, T. Hikosaka, and M. Yanagawa, Heteroatom Chem., 3, 563 (1992). 

1 The Catellani Reactions using Norbomene as a Template for ortAo-Substitution 

In continuing studies on Pd-catalyzed reactions of norbomene (1), Catellani has discovered very interesting reactions, in which norbomene shows unique behavior [1]. Catellani and co-workers carried out a three-component reaction of iodobenzene, methyl acrylate, and n-butyl iodide in the presence of 1 equivalent of norbomene (1), and obtained methyl 2,6-di-n-butylphenylacrylate (2) in 93 % yield using cw-exo-2-phenylnorbomylpalladium chloride as a catalyst. Norbomene (1) was recovered after the reaction [2]. No direct Heck reaction of iodobenzene with acrylate occurred showing that the strained double bond in norbomene undergoes insertion much faster than that of acrylate. The behavior of norbomene (1) is tmly remarkable. 

This reaction revealed several very interesting and unexpected (or curious) steps. The meehanistic explanation given by Castellani can be summarized in the following seheme. First, syn insertion of 1 to Ph-Pd-I affords the cis, exo complex 3. In this ease, syn f-H elimination to give phenylnorbomene is impossible due to the rigid trans configuration of the Pd atom and -hydrogen. The 

The reaction of o-iodotoluene (11) with acrylate and a large excess of n-PrI in the presence of 1 proceeded more efficiently using ligandless Pd(OAc)2, and 2-methyl-6-n-propylphenylacrylate (12) was obtained [3]. 

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Miscellaneous Coupling Reactions of Aryl Halides with N-Nucleophiles. 188... 

Other miscellaneous syntheses that have benefited from the introduction of dppf to the catalytic mixture include the coupling reactions of aryl triflates or halides with ketene trimethylsilyl acetals [165], The catalyst mixture is [Pd(OAc)(i -C4H7)]2/LiOAc/phos-phine. In this case, nucleophilic activation of the Si-O bond of the acetal enables an Si-Pd transmetalation to give a a-complex 52 without necessitating a phosphine... 

Miscellaneous Processes. A convenient procedure for the palladium-catalyzed conversion of aryl halides into the corresponding nitrile has been devised. Previously observed catalyst deactivation by the cyanide ion is avoided through slow release of (soluble) cyanide in the form of acetone cyanohydrin that is introduced into the reaction mixture by syringe-pump. This procedure has been refined through the development of a ligand-free catalyst system and by utilizing potassium ferricyanide as... 

Miscellaneous Methods of Preparing Phosphines. Palladium-catalysed formation of phosphorus-carbon bonds continues to be developed as a useful route to organophosphines. The reactions of primary or secondary phosphines with aryl- or vinyl-halides in the presence of a palladium catalyst, usually palladium acetate or a zerovalent palladium-phosphine complex, have been used in the synthesis of steroidal phosphines, e.g., (128), the cationic diphosphine system... 

The reaction of thienyllithium with organic halides to form C—C bonds has been discussed in Section 2.10.4.7.2. This cannot, however, be extended to aryl, alkenyl or heteroaryl halides in which the halogen is attached to an sp carbon. Such cross-coupling can be successfully achieved by nickel or palladium-catalyzed reaction of the unsaturated organohalide with a suitable thienyl metal derivative. The metal is usually zinc, magnesium, boron or tin occassionally lithium, mercury, copper, and silicon derivatives of thiophene have also found application in such reactions. In addition to this type, the Pd-catalyzed reaction of halogenated thiophenes with suitable alkenes and alkynes, usually referred to as the Heck reaction, is also discussed in this section. Besides these, a few other miscellaneous Pd-catalyzed substitution reactions on thiophene will also be referred to. 

Cross-coupling reactions of miscellaneous arylmetalllc Mn, Ti, In, and Ge reagents with aryl halides and sulfonates... 

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