Triene rhodium complexes

The dimerization of 19 also occurs in the presence of rhodium salts with stable crystalline rhodium complexes of 19 that can be isolated.26 it is interesting to note that the thermal dimerization of 19 gives only a 25% yield of the cyclodimer 20.27 The metal-catalyzed dimerization of cyclohepta-l,2,3-triene in the presence of tetrakis(triphenylphosphane)nickel(0) gives tricyclic 4-radialene 21.28 The structure of this cydobutane was confirmed by X-ray diffraction. 

COBALT AND RHODIUM COMPLEXES DERIVED FROM OFCOT AND PERFLUOROBICYCLO[4.2.0]OCTA-2,4,7-TRIENE... 

Furthermore, an enantioselective cycloaddition was observed when the carbenoid was formed by the use of a chiral rhodium complex 37 derived from (S)-N-para (ferf-butylbenzene)sulfonylprolinate (TBSP). For example, decomposition of 38 by 37 in the presence of furan generated 39 with 80% ee, along with a triene containing side-product in 15-20% yield, Eq. 25. However the ee dropped significantly when other vinyldiazo compounds were studied under analogous conditions. 

Via intermediates Cycloocta-1,5-diene from -1,3,5-triene ring via rhodium complexes... 

Triene complexes of rhodium have been prepared by a crossed aldol condensation with acetophenone (211) or by Wittig reactions [Eq. (29)] (212). 

Suitable a, tw-enynes can be cyclized when allowed to react with catalytic quantities of [RhCl(PPh3)3]. Alken-2-ynes do not react and the yield is greatly diminished in the case of alk-2-enyne substrates. However, substitution of the alkene bond does not appear to inhibit the dicyclization of dienynes or the cyclization of alkynenones. The dienyne s reaction, shown in equation (21), is catalyzed more effectively by rhodium(I) complexes containing tertiary phosphite ligands. Under similar conditions, trienes can also be cyclized. The cyclopropyl ring can serve as an alkene bond precursor in cyclizations (equation 22). ... 

Bicyclo[6.1.0]nona-2,4,6-triene and the 9-methyl-substituted analog 35 were complexed with (trifluoroacetylacetonato)rhodium(I) [(tfacac)Rh(I)] and selectively hydrogenated to form bicyclo[6.1.0]nona-2,6-diene complexes 37, which upon decomplexation underwent Cope rearrangement to give bicyclo[5.2.0]nona-2,5-dienes 39. The parent compound 38 (R = H) and the u t/-9-methyl derivative rearranged above 0 °C, while the ij n-9-methyl- and the 9,9-dimethyl system 38 (R = Me) require 150°C for this transformation. The stereochemistry of these conversions was investigated with deuterium-labeled analogs. ... 

Brummond s group [23] and independentlythe group of Shibata [24] discovered that rhodium(I) complexes are excellent catalysts in the formal Alder-ene cycloisomerization of allenynes to give cross-conjugated trienes under mild conditions... 

However, in the latter case, a cationic rhodium(I) complex had to be added to catalyze the intramolecular Diels-Alder reaction with the triene moiety to give a diene, ready for an intermolecular [4 -I- 2] cycloaddition. Strictly speaking, this case is definitely a borderline one with respect to the rigorous definition given in the introduction. 

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