Rhodium catalyzed intermolecular

The rhodium-catalyzed intermolecular hydrative dimerization of 1-alkynes leads to a,/3-unsaturated ketones (Equation (190)).154... 

In 1981 it was shown that rhodium(II) carboxylates smoothly catalyze the addition of ethyl diazoacetate to a variety of alkanes11. While some differentiation between possible sites of insertion was observed, selectivity is not as high for this carbenoid process as it is for the free radical process above. Rhodium-catalyzed intermolecular C-H insertion is thought to proceed via electrophilic addition of an intermediate rhodium carbene into the alkane C—IT bond. 

The rhodium-catalyzed intermolecular cyclopropanation of diazobutenoates with benzo[/ ]furan 82 resulted in the formation of a benzo [ Jfuran-derived cyclopropane in a diastereo- and enantioselective manner, as depicted in Equation (75) <1998JOC6586>. 

Recently, efficient rhodium-catalyzed intermolecular C—H amination reactions have been reported where a sulfonimidamide is used as the nitrene precursor [46]. The functionalizations of various C—H bonds proceed smoothly in this type of intermolecular amidation reaction (Equation 11.20) [47]. When chiral sulfonimida-mides are used, moderate to excellent diastereoselectivities can be achieved. 

Transition metal catalyzed intermolecular carbocyclization has been used in the construction of six-membered ring systems (10, 352) and provides a powerful approach to the construction of complex polycyclic systems. The rhodium-catalyzed intermolecular [2 - - 2 - - 2] carbocychzation of heteroatom-tethered 1,6-enynes with symmetrical and unsymmetrical alkynes affords the corresponding bicyclohexadienes in a highly efficient and regioselective... 

Rhodium-Catalyzed Intermolecularly Generated Carbonyl Ylides. 152... 

A series of l-benzazepin-5-ones were furnished via a rhodium-catalyzed intermolecular hydroacylation of an allyl amine onto an aryl aldehyde (14AGE3688) while a one-step synthesis of a number of tetrahydro-3-benzazepines was achieved through the palladium-mediated reaction of phenylethylamines with allenes (14JOC9578). 

Rhodium-Catalyzed Intermolecular Amidation of Arenes with Sulfonyl Azides... 

Wender s group has also developed rhodium-catalyzed intermolecular [5-1-2] cycloadditions. At first, they found the catalysis system of Rh(PPh3)3Cl for the intramolecular reactions was not effective at all for the intermolecular reactions. To effect the intermolecular [5-1-2] cycloadditions, [Rh(CO)2Cl]2 must be used and oxygen substitution of the cyclopropane was necessary (see (17)) [37-39]. Then they successfully expanded the substrate to unactivated vinylcyclopropanes by adjusting the substituents. For monosubstituted alkynes, the substitution on the olefin terminus directs the formation of single isomer that minimized steric hindrance (see (18)) [40]. The [5-1-2] cycloadditions can also be applied to VCPs with allenes (see (19)) [41]. It should be noted that the alkyne substituent did not interfere with the reaction, indicating that allenes as reaction partners were superior to alkyne in the [5-1-2] cycloadditions. Curiously, the authors didn t report the corresponding intermolecular [5-1-2] cycloadditions of VCPs with alkenes. 

Bergman and Ellman developed a rhodium-catalyzed intermolecular reaction between a broad number of heterocycles andavariety of alkenes. Benzimidazole, benzothiazole, and benzoxazole (154) underwent facile intermolecular alkylation with neohexene to afford heterocyclic products 155-157 in high yields (Scheme 10.54). Substitution of either coupling parmer with electron-rich or electron-deficient functional groups did not affect the efficiency of the reaction. 

Scheme 7.10 Rhodium-catalyzed intermolecular cross-lrimerization.

Parallel investigations of the rhodium-catalyzed intermolecular reaction have shown that, at first glance, its mechanism is identical in aU respects to the intramolecular process. " The Hammett analysis ip = — 0.73 vs. the... 

In 2009, Hayashi and co-workers reported on a rhodium-catalyzed intermolecular asymmetric hydrosulfenylation of diphenylphosphinylallene 251 using benzenethiol and naphthalene-2-thiol (Scheme 46.30). The reaction proceeded with good yields and enantioselectivities, demonstrating the feasibility of asymmetric thiofunctionalization of allenes using a chiral phosphine ligand 252. 

Scheme 2.47 Rhodium-catalyzed intermolecular double [2-1-24-2] cycloaddition...

Tanaka, K., Fukawa, N., Suda, T. and Noguchi, K. (2009) One-step construction of five successive rings by rhodium-catalyzed intermolecular double [2+2+2] cycloaddition enantioenriched [9]helicene-like molecules. Angewandte Chemie International Edition, 48(30), 5470-5473. 

Murakami, M., Ubukata, M., Itami, K. and Ito, Y. (1998) Rhodium-catalyzed intermolecular [4-1-2] cycloaddition of unactivated substrates. Angewandte Chemie International Edition, 37(16), 2248-2250. 

The rhodium-catalyzed tandem carbonyl ylide formation/l,3-dipolar cycloaddition is an exciting new area that has evolved during the past 3 years and high se-lectivities of >90% ee was obtained for both intra- and intermolecular reactions with low loadings of the chiral catalyst. 

Diastereoselective syntheses of dihydrobenzo[f>]furans have been accomplished by a rhodium-catalyzed regioselective and enantiospecific intermolecular allylic etherification of o-iodophenols as a key step, providing the corresponding aryl ally ether 122, which leads to a dihydrobenzo[b]furan by treatment of the intermediate aryl iodide with tris(trimethylsilyl)silane and triethylborane at room temperature in the presence of air <00JA5012>. 

However, the decarbonylation reaction can be suppressed by the use of specially tailored chelating groups. Intermolecular processes involving dienes and salicylaldehydes are now known, and are thought to proceed via a double chelation mechanism, akin to the Jun-type system. Rhodium-catalyzed reactions lead to hydroacylated products, under relatively mild conditions (Equation (134)).117... 

The preparation of cyclopropanes by intermolecular cyclopropanation with acceptor-substituted carbene complexes is one of the most important C-C-bond-forming reactions. Several reviews [995,1072-1074,1076,1077,1081] and monographs have appeared. In recent decades chemists have focused on stereoselective intermolecular cyclopropanations, and several useful catalyst have been developed for this purpose. Complexes which catalyze intermolecular cyclopropanations with high enantiose-lectivity include copper complexes [1025,1026,1028,1029,1031,1373,1398-1400], cobalt complexes [1033-1035], ruthenium porphyrin complexes [1041,1042,1230], C2-symmetric ruthenium complexes [948,1044,1045], and different types of rhodium complexes [955,998,999,1002-1004,1010,1062,1353,1401-1405], Particularly efficient catalysts for intermolecular cyclopropanation are C2-symmetric cop-per(I) complexes, as those shown in Figure 4.20. These complexes enable the formation of enantiomerically enriched cyclopropanes with enantiomeric excesses greater than 99%. Illustrative examples of intermolecular cyclopropanations are listed in Table 4.24. 

In the first rhodium-catalyzed carbonylative silylcarbocyclization (CO-SiCaC), which was reported in 1992 [12, 13], silylcyclopentenone 9 was isolated as a minor product in the silylformylation of 1-hexyne 8 (Scheme 7.4). Under optimized conditions using Et3SiH and ( BuNC)4RhCo(CO)4 as the catalyst at 60°C, 9 is formed in 54% yield [13]. A possible mechanism proposed for this intermolecular CO-SiCaC is shown in Scheme 7.4 [13]. In this mechanism, the formation of 9 is proposed to proceed via in-... 

The first example of an intermolecular enantioselective rhodium-catalyzed aUylic alkylation, relying on the phosphito-thioether ligands 58 and 59 and the P,N-ligand 60 (Scheme 10.12), was reported by Pregosin and co-workers in 1999 [55]. The in-situ... 

Matsuda and co-workers described the first intermolecular rhodium-catalyzed [4-1-2] reaction in 1987 [5]. Consistently with the other transition metal catalysts that had been developed for similar systems, the rhodium-catalyzed version was also limited to... 

Tab. 12.9 Scope of the intermolecular rhodium-catalyzed [4-I-2-I-2] carbocyclization reaction.

Recent advances in the rhodium-catalyzed [4-1-2] reactions have led to the development of the first highly regioselective intermolecular cyclization, providing access to new classes of carbocycles with both activated and unactivated substrates. The chemo- and stereoselective carbocyclizations of tethered diene-allene derivatives afford new classes of 5,6- and 6,6-bicyclic systems. Additionally, examination of a wide range of factors that influence both diastereo- and enantioselectivity has provided a significant advance in the understanding of catalyst requirements across these systems. 

The ability to produce 1,3-dipoles, through the rhodium-catalyzed decomposition of diazo carbonyl compounds, provides unique opportunities for the accomplishment of a variety of cycloaddition reactions, in both an intra- and intermolecular sense. These transformations are often highly regio- and diastereoselective, making them extremely powerful tools for synthetic chemistry. This is exemplified in the number of applications of this chemistry to the construction of heterocyclic and natural-product ring systems. Future developments are likely to focus on the enantioselective and combinatorial variants of these reactions. 

The intermolecular version of the above reaction has also been reported (391). In the first example, a rhodium-catalyzed carbonyl yhde cycloaddition with maleimide was smdied. However, only enantioselectivities of up to 20% ee were obtained... 

Ishiyama and Hartwig disclosed a set of rhodium(I)-catalyzed intermolecular Heck-type reactions between aryl iodides and N-heterocyclic aldimines to form the corresponding ketimines. Ishiyama T, Hartwig J (2000) 122 12043... 

In 1980, Miller et al. [76] reported the first example of an intermolecular hydroacylation of an aldehyde with an olefin to give a ketone, during their studies of the mechanism of the rhodium-catalyzed intramolecular cyclization of 4-pentenal using ethylene-saturated chloroform as the solvent. Later James and Young [77] reported that the reaction of propionaldehyde with ethylene can be conducted in the presence of RuCl2(PPh3)3 as the catalyst without any solvent at 210 °C, resulting in the formation of 3-pentanone in 2-4% yield (turnover number of 230) (Eq. 49). 

Intermolecular [3+2] 1,3-dipolar cycloaddition of a D-glyceraldehyde-derived nitrile oxide to the 4,5-double bond of 2-methylfuran gave a 60 40 diastereomeric ratio of the two furoisozaxoline isomers. This chemistry was employed in the synthesis of L-furanomycin <2005EJ03450>. As depicted in Scheme 43, an intramolecular cycloaddition of a furan with a carbonyl ylide dipole proceeded under rhodium-catalyzed microwave-promoted conditions to provide the cycloadduct in a modest yield <20040L3241>. 

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