Rhodium-catalysed reactions cycloaddition

Among reactions of phosphines occurring in the coordination sphere of a transition metal are a rhodium-catalysed hydrogenation and silylation of P-P bonds to give secondary phosphines and silylphosphines, a chiral amine-palladium template-promoted asymmetric cycloaddition of phenyldivinylphosphine to 3,4-dimethyl-1-phenylarsole to give the chiral... 

The formal 2 -I- 2-cycloaddition reaction of platinum(ll) acetilides (14) with TCNE and TCNQ initially produced 7,7,8,8-tetracyano-p-quinodimethane cyclobuta-1, 3-dienes that undergo retroelectrocyclization to produce feis-cycloadducts (15, 16). In all examples investigated, the triple bond adjacent to the platinum atom did not react with the TCNE or the TCNQ (Scheme 5). The 2-I-2-cycloaddition of substituted cyclobutadiene-AlCl3 complexes (18) with methyl phenylpropynoate (17) produced Dewar benzene intermediates (19) that readily converted to 1,2,3,4-tetramethyl- and 1,2,3,4-tetraethyl-fluorenes (20) (Scheme 6). The first rhodium-catalysed inter-molecular 2-1-2-cycloaddition of terminal alkynes with e-deflcient alkenes yielded substituted cyclobutenes in high yields (99%) and complete regioselectivity. An 8-quinolinolatorhodium/phosphine catalyst (21) was employed in this reaction. ... 

Dinitrogen-fused heterocycles have been formed in high yield by thermal 3-1-2-cycloadditions of two types of azomethine imines with allenoates. Rhodium-catalysed formal 3 -l- 2-cycloadditions of racemic butadiene monoxide with imines in the presence of a chiral sulfur-alkene hybrid ligand have furnished spirooxindole oxazolidines and 1,3-oxazolidines stereoselectively. ° Formation of 1,2-disubstimted benzimidazoles on reaction of o-phenylenediamine with aldehydes is promoted by fluorous alcohols that enable initial bisimine formation through electrophilic activation of the aldehyde. 

Two different types of tandem reactions for the synthesis of highly functionalized cyclohexenones cyclopropyl-substituted propargyl esters initiated rhodium-catalysed Saucy-Marbet 1,3-acyloxy migration have been reported (Scheme 152). The resulting cyclopropyl-substituted allenes derived from acyloxy migration followed by 5 -f 1-cycloaddition with carbon monoxide. ... 

The greater part of this chapter is concerned with the Diels-Alder and hetero-Diels-Alder reaction. The asymmetric version of both of these reactions can be catalysed with metal-based Lewis acids and also organocatalysts. The catalytic asymmetric 1,3-dipolar cycloaddition of nitrones and azomethine ylides is also discussed. Again, most success in this area has been achieved using metal-based Lewis acids and the use of organocatalysts is begiiming to be explored. This chapter concludes with a brief account of recent research into the asymmetric [2+2]-cycloaddition, catalysed by enantiomerically pure Lewis acids and amine bases, and also the Pauson-Khand [2- -2- -l] cycloaddition mediated by titanium, rhodium and iridium complexes. 

A rhodium(III)-catalysed oxidative C-H/N-H activation/annulation sequence has been developed for the addition of NH-sulfoximines (117) to acetylenes (118), providing 1,2-benzothiazines (119). The re-oxidation of the rhodium catalyst is attained in the presence of a catalytic amount of (AcO)2pe with oxygen as a terminal stoichiometric oxidant. In a similar way, the Ru(lll)-catalysed ortho-directed C-H activation of hydrazones (120), followed by cycloaddition to acetylenes (118), resulted in the formation of isoquinolines (121) upon the concomitant cleavage of the N-N bond. The reaction did not require an external oxidant. ... 

The 3 -I- 2-cycloaddition reactions of A-alkylsufonylimines with alkenes, enamines, ynamines, diazo compounds, azirines, silyloxydienes, and azadienes have been extensively reviewed. Rhodium(III)-catalysed cycloaddition of cyclic sulfonylketimines with internal alkynes afforded multifunctional spirocyclic sultam products in high... 

Scheme 3.5 Domino carbonyl ylide formation-l,3-dipolar cycloaddition reaction catalysed by a combination of rhodium catalysis and chiral nickel catalysis.

Reviews.—Recent reviews involving olefin chemistry include olefin reactions catalysed by transition-metal compounds, transition-metal complexes of olefins and acetylenes, transition-metal-catalysed homogeneous olefin disproportionation, rhodium(i)-catalysed isomerization of linear butenes, catalytic olefin disproportionation, the syn and anti steric course in bi-molecular olefin-forming eliminations, isotope-elfect studies of elimination reactions, chloro-olefinannelation, Friedel-Crafts acylation of alkenes, diene synthesis by boronate fragmentation, reaction of electron-rich olefins with proton-active compounds, stereoselectivity of carbene intermediates in cycloaddition to olefins, hydrocarbon separations using silver(i) systems, oxidation of olefins with mercuric salts, olefin oxidation and related reactions with Group VIII noble-metal compounds, epoxidation of olefins... 

A review describing the recent advances in transition-metal-catalysed 2-I-2-1-2-cyclotrimerization reactions has been published. A cationic rhodium (I)/(l )-Hg-BINAP complex catalysed the 2-I-2-I-2-cycloaddition reaction of 1,6-enynes with acrylamides to synthesize annulated cyclohexenes in high yields and excellent... 

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