Complexes cyclization

Uemura M (2004) (Arene)Cr(Co)3 Complexes Cyclization,Cycloaddition and Cross Coupling Reactions. 7 129-156 Ujaque G, see Drudis-Sole G (2005) 12 79-107... 

Finally, a few cyclizations of unsaturated side chains on o-halogeno-anilines or -benzenes have been catalyzed by transition metal complexes. Cyclization of the cinnamylbenzylamine (245) by palladium gives some 4-benzylisoquinoline and some of compound (246) (77TL1037). Acryloylanilines (247) and (248) can be cyclized by a nickel complex (75MI20800) or by a palladium complex (79JA5281). The mechanism for the latter reaction is given in equation (50). 

The chromium complex cyclizes to a 5-membered complex (vi), which loses ethylene and the metal (vii), to give methoxycyclopentadienone. Subsequent reduction (viii) under the reaction conditions by Cr(0)-H2O affords the methoxycyclopentenone. The correspond-... 

Saxitoxin occurrence, 5, 604 Saxitoxiri, hydroxy-occurrence, 5, 604 Scholtz synthesis indolizines, 4, 466 Scillaren A occurrence, 3, 883 Scutellarein chemistry, 3, 697 Secobarbital, 3, 150 1,19-Secocorrin nomenclature, 1, 30 A/D-Secocorrin complexes cyclization, 4, 429 A/D-Secocorrin, Al8-dehydro-synthesis, 4, 429 A/D-Secocorrin, 1-oxo-synthesis, 4, 429 Secocorrins... 

The anionic complexes (50) are obtained from the group VI carbonyl and the dilithium derivatives of the hydroxyalkynes HC=CCR2(OH) subsequent protonation or acylation affords propadienylidene (51) or carbene (52) complexes by complex cyclization and addition reactions (Scheme 3) (28). Attempts to obtain the dimethyl complex by reaction of the chromium alkynolate dianion with COCl2 gave only polymeric material. More stable complexes were obtained with R = aryl (73). 

If an [Os]-anisolium complex bears a proton at C4 (63, Scheme 7), exposure to DIEA at low temperature results in a kinetic deprotonation of the benzylic carbon attached to C3 generating the extended vinyl ether 64. This complex cyclizes under Lewis addic conditions to generate an anisolium ion, which can then be deprotonated at C4 to generate a tetralin complex [25]. Heating this species liberates the tetralin 65 in 39 % yield (based on 63). 

Enyne metathesis catalyzed by ruthenium carbene complexes (cyclization of enynes to heterocycles combination of metathesis with cycloaddition leading to the formation of heterocycles) 03S1. 

Cyclization of aldehyde olefin 94 was also investigated, and was found to lead to a 1 1 mixture of bridged products 99 and 100 (Scheme 18). This transformation probably occurs through sulfonyl imine Lewis acid complexes cyclizing via conformations 95 and 96 to carbonium ions 98 and 97, respectively. Proton elimination from these intermediates would afford the observed epimeric sulfonamide alkenes. 

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