Alkylation, palladium-catalysed

Indoles with carbocyclic halogen or triflate substituents are potential starting materials for vinylation, arylation and acylation via palladium-catalysed pro-cesses[l]. Indolylstannanes. indolylzinc halides and indolylboronic acids are also potential reactants. The principal type of substitution which is excluded from such coupling reactions is alkylation, since saturated alkyl groups tend to give elimination products in Pd-catalysed processes. 

By analogy with modern routes for the preparation of well-defined polyanilines (D ), palladium-catalysed cross coupling of 1,4-diiodobenzene and primary aryl- and alkyl-phosphines affords the comparatively short chain polymers (66a-c) (Mn= 1000-4000) (Scheme 20), that can be oxidised either by atmospheric... 

In 1999, Ikeda et al. reported a new type of sulfur-oxazoline ligands with an axis-fixed or -unfixed biphenyl backbone prepared in good yields by coupling reactions of methoxybenzene derivatives substituted with a chiral oxazoline and a sulfur-containing Grignard reagent. These ligands were subsequently evaluated for the test palladium-catalysed asymmetric allylic alkylation... 

These workers have developed another new type of chiral S/N ligands, namely aziridine sulfides, which were easily synthesised in a straightforward synthetic route from inexpensive and readily available (i )-cysteine. The efficiency of this sterically and electronically varied set of ligands was then examined as chiral catalysts in the palladium-catalysed test reaction. The alkylated product was obtained in excellent yields and stereoselectivities of up to 99% ee, as shown in Scheme 1.44. 

Moreover, a few chiral ferrocenylsulfur-imine ligands were investigated in the palladium-catalysed asymmetric allylic alkylation of 1,3-diphenylpropenyl acetate and cyclohexenyl acetate with dimethyl maionate (Scheme... 

A tandem palladium-catalysed ort/io-alkylation/intramolecular Heck reaction coupling sequence was used effectively to access in fair yields the tetrahydro 1-benzoxepines 67 from the iodoaryl precursor 66 and the appropriate alkyl bromide. The norbornene plays a relay role in the proposed reaction cycle <06JOC4937>... 

Figure 6.18. Palladium catalysed allylic alkylation using fluorinated ligands.[60, 61]...

A diastereoselective imine alkylation and a palladium-catalysed biaryl coupling were important steps in the diastereoselective synthesis of 6,7-dihydro-5//-dibenz[c,e]azepines (Scheme 7) starting from (R)-l-(2-methoxyphenyl)ethylamine. Selection for the... 

The palladium catalysed sequential alkylation-alkenylation of 5-iodoquinoline leads to the formation of the quinolooxepin ring system (5.20.), The process, closely related to the Catellani reaction,19 runs through an ort/zo-alkylation - Heck reaction sequence. The preparation of a series of benzoxepines has also been achieved in this manner, starting from such iodobenzene derivatives, where one of the or/7 o-positions was blocked by substitution.20... 

H. H. Baer and Z. S. Hanna, The preparation of amino sugars and branched-chain sugars by palladium-catalysed allylic substitution of alkyl hex-2-enopyranosides, Can. J. Chem. 59 889 (1981). 

A number of methods for the preparation of vinyl and allyl sulfones are available [1U9, 110], and the syntheses of vinyl sulfones from alkenes has been reviewed [116]. A simple one-step procedure of wide applicability makes use of a palladium-catalysed cross-coupling reaction between aryl and alkyl sulfonyl chlorides and substituted vinyl and allyl stannanes... 

Bremberg, U., Larhed, M., Moberg, C. and Hallberg, A., Rapid microwave-induced palladium-catalysed asymmetric allylic alkylation, J. Org. Chem., 1999, 64, 1082-1083. 

Evans, RA. and Brandt, T.A., Enantioselective palladium-catalysed allylic alkylation using E- and Z-vinylogous sulfonates, Org. Lett., 1999, 1, 1563-1565. 

The enantioselective palladium-catalysed decarboxylative allylic alkylation has been highlighted.50... 

Thus the alkyl ester end groups of convergently grown poly(benzyl ether) dendrimers can be subjected to post-synthetic modification by hydrolysis [28], reduction [29], transesterification/amidation [28] in a variety of ways. Subsequent modification of poly(benzyl ether) dendrons bearing p-bromobenzyl end groups by palladium-catalysed coupling reactions permitted preparation of dendrons with phenyl, pyridinyl, or thiophenyl end groups [30]. 

The Suzuki Coupling, which is the palladium-catalysed cross coupling between organoboronic acid and halides. Recent catalyst and methods developments have broadened the possible applications enormously, so that the scope of the reaction partners is not restricted to aryls, but includes alkyls, alkenyls and alkynyls. Potassium trifluoroborates and organoboranes or boronate esters may be used in place of boronic acids. Some pseudohalides (for example triflates) may also be used as coupling partners. 

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