Cyclizations tetrakis palladium

Dialkylindolines and 1,3-dialkylindoles are formed in poor yield (<10%) from the reaction of ethyl- or phenymagnesium bromide with 2-chloro-N-methyl-N-allylaniline in the presence of catalytic quantities of (bistriphenylphosphine)nickel dichloride.72 In a modification of this procedure, the allyl derivatives can be converted by stoichiometric amounts of tetrakis(triphenylphosphine)nickel into 1,3-dialkylindoles in moderate yield72 (Scheme 43) an initial process of oxidative addition and ensuing cyclization of arylnickel intermediates is thought to occur. In contrast to the nickel system,72 it has proved possible to achieve the indole synthesis by means of catalytic quantities of palladium acetate.73 It is preferable to use... 

V-(2 -bromobcnzyl)-2-methylindole derivatives were cyclized relatively easily to pyrrolophenantridines in the presence of tetrakis(triphenyl-phosphino)palladium (4.29.). In the absence of the 2-methyl group the intramolecular attack of the intermediate arylpalladium complex is directed at the five membered ring giving indoloisoquinoline.33... 

Several (A/-alkenyl)iodoacetamides undergo cyclization when they are reacted with tetrakis(triphe-nylphosphine)palladium(O). The highest yields (which are generally only moderate) are obtained in DMF solution with 1,8-dimethylaminonaphthalene (Proton Sponge) to take up the hydrogen iodide formed. This reaction has been used to prepare piperidones, oxindoles, indolizidines, quinolizidines, pyrrolidines, indoles, quinolines53 and pyrrolizidines (equation 18).54... 

Homoallyl chloroformates cyclize catalytically to a-methylene- y-butyrolactones in moderate yields at 130 C with tetrakis(triphenylphosphine)palladium(0) (equation 44).l0s This reaction only gives 1-2% of product when it is carried out intermolecularly. The presumed intermediate in the homoallyl chlorofor-mate cyclization has been isolated and kinetic measurements show that that cyclization is inhibited by an excess of triphenylphosphine. A chelated ir-alkene intermediate is proposed.1 6... 

Carboline synthesis. The 3-amino-4-(o-bromophenyl)pyridine 1 cyclizes to the (3-carboline 2 in the presence of tetrakis(triphenylphosphine)palladium(0) (1.2-1.5 equiv.,... 

NAZAROV CYCLIZATION Aluminum chloride. Benzylchlorobis(triphenylphos-phine)palladium. Bis(acetonitrile)-dichloropalladium(II). Boron trifluoride etherate. Tetrakis(triphenyl-phosphine)paIladium. 

An intramolecular aryl guanidinylation was reported by R. A. Batey and G. Evindar.106 They found palladium tetrakis worked well for this cyclization, but catalytic Cul and 1,10-phenanthroline exhibited broader scope and lower loadings. 

The 2-bromododeca-l,ll-dien-6-yne derivative 461 undergoes a triple cyclization, followed by rearrangement, under the influence of a palladium catalyst to yield 462. Cross-coupling of the iodo compound 463 with ( )-l-hexen-l-ylzinc chloride in the presence of tetrakis(triphenylphosphine)palladium yields 68% of the indane 464 and 19% of the uncyclized product 465 ". ... 

A general cyclization reaction of 6-lithiated (trimethylsilyl)alkynes is exemplified by the conversion of the iodo compound 499 into the methylenecyclopentane 500 by treatment with -butyllithium . Heating a mixture of the acetylenic silane 501 and 2-(benzyloxymethyl)allylzinc bromide 502 resulted in the diene 503, which cyclized to the methylenecyclopentene 504 in the presence of tetrakis(triphenylphosphine)palladium ... 

CYCLIZATION Benzeneselenenyl bromide. T etrakis(triphenylphosphine)-palladium(O). Tetrakis(triphenylphos-phine)palladium-l,3-Bis(diphcnylphos-phinejpropane. Thallium(III) trifluoroacetate. 

Enantiomerically pure epoxide 307 was synthesized in 16 steps from D-(-)-quinic acid, an inexpensive plant metabolite. Intramolecular cyclization was observed with a catalytic amount of tetrakis(triphenylphosphine)palladium(0) at 25 °C to afford the optically active isoquinuclidine in 95% yield. The introduction of alkyl groups, such as the ethyl group of ibogamine and catharanthine, can easily be accompUshed at the epoxy ketone stage. 

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