Cyclopropane-Aldehyde -Cycloadditions

More recently, Karadedian and Kerr have applied the successful cyclopropane/aldehyde cycloaddition reaction in the asymmetric synthesis of (+)-isatisine A starting from the homochiral (5)-vinylcyclopropane diester [40a,b], A close examination of isatisine A revealed that the stereochemistry between and of the tetrahydroftiran could be achieved through a cycloaddition reaction starting from the S cyclopropane. 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

The meso-ionic 1,3-oxazol-S-ones show an incredible array of cycloaddition reactions. Reference has already been made to the cycloaddition reactions of the derivative 50, which are interpreted as involving cycloaddition to the valence tautomer 51. In addition, an extremely comprehensive study of the 1,3-dipolar cycloaddition reactions of meso-ionic l,3-oxazol-5-ones (66) has been undertaken by Huisgen and his co-workers. The 1,3-dipolarophiles that have been examined include alkenes, alkynes, aldehydes, a-keto esters, a-diketones, thiobenzophenone, thiono esters, carbon oxysulfide, carbon disulfide, nitriles, nitro-, nitroso-, and azo-compounds, and cyclopropane and cyclobutene derivatives. In these reactions the l,3-oxazol-5-ones (66)... 

The Lewis acid-catalysed 3 + 2-cycloaddition of cyclopropanes with aldehydes yields tetrahydrofurans with high diastereoselectivity.22 The enantiospecific Sn(II)-and Sn(IV)-catalysed formal 3 + 2-cycloadditions of aldehydes with donor-acceptor (g) cyclopropanes produce optically active tetrahydrofurans23 The bulky phosphites and phosphoramidites are excellent ligands which promote the Pd-catalysed 3 + 2-intramolecular cycloaddition between alkylidenecyclopropanes and alkynes24 The... 

Metal complexes enable one to employ molecules that are thermally unreactive toward cycloadditions by taking advantage of their ability to be activated through complexation. Most of the molecules activated by transition-metal complexes involve C-C unsaturated bonds such as alkynes, alkenes, 1,3-dienes, allenes, and cyclopropanes. In contrast, carbonyl functionalities such as aldehydes, ketones, esters, and imines seldom participate in transition-metal-catalyzed carbonylative cycloaddition reactions. Recently, such a transformation was reported via the use of ruthenium complexes. 

Acetals from a,/3-unsaturated aldehydes and optically active 1-aryl-1,3-propanediols are cyclopropanated by the diiodomethane/diethylzinc reagent with moderate selectivity69. After oxidative cleavage of the auxiliary, cyclopropanecarboxylic acids are obtained with 21 -78% ee. Thus, the C2-symmetric auxiliaries seem to be superior for this kind of [2 + 1] cycloaddition. 

The generation of carbenes from tosylhydrazones of thiophene aldehydes, and their reactivity have been discussed in CHEC-I, <84CHEC-I(4)74i>. A few further reactions of such carbenes have been reported. In presence of acrylonitrile, the product could be either the cyclopropane (484) (from the carbene) or the pyrazoline (485) (by cycloaddition of the diazo intermediate) <88H(27)ll4i>. The carbene can similarly be trapped by cis and trans stilbene, dimethyl fumarate or maleate to form the respective cyclopropanes <87BCJ4317>. 

Cycloaddition of cyclopropanes to aldehydes leads to the formation of tetrahydrofurans derivatives, whose enantiomeric form can be obtained either by using enantioenriched cyclopropane substrates or by a dynamic kinetic asymmetric transformation. In this regard, Johnson et al. reported a dynamic kinetic asymmetric [3 -I- 2] cycloaddition of racemic cyclopropanes 63 for the enantioselective synthesis of tetrahydrofurans 64. In this study, the magnesium catalyst can promote the ring opening of the racemic cyclopropane and catalyses the reaction of one of the ring-opened enantiomers with the aldehydes (Scheme 3.19). 

The AlCl3-catalysed 3-I-2-cycloaddition of diethyl frans -2,3-disubstituted cyclopropane-1,1-dicarboxylates and aromatic aldehydes produced diethyl 2,5-diaryl-4-benzoyltetrahydrofuran-3,3-dicarboxylates in moderate to good yields and with excellent diastereo-selectivities. The palladium-catalysed 3 -f- 2-cycloaddition of trimethylenemethane with aldehydes produced methylenetetrahydrofurans in good yields and with good enantioselectivities. A novel phosphoramidite ligand possessing a stereogenic phosphorous (29) was used in this transformation. ... 

Kerr and coworkers developed an elegant access to optically active 3,6-cis disubstituted oxazine ring system via a homo-l,3-dipolar cycloaddition reaction of an aldehyde, a hydroxylamine, and a cyclopropane in the presence of a Lewis acid (Scheme 16). To emphasize the usefulness of this reactivity, it was first applied to the synthesis of phyllanthidine (7) (vide infra. Scheme 33). A modified version of this reaction provided access to 2,5-disubstituted pyrroloisoxazohdines, which upon N—O bond cleavage efficiently furnished the corresponding 2,5-cis pyrrofidine ring system (Scheme 16). 

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