Rhodium-catalyzed intramolecular

Oshima et al. explored a cationic rhodium-catalyzed intramolecular [4+2] annulation of l,3-dien-8-ynes in water in the presence of sodium dodecyl sulfate (SDS), an anionic surfactant.132 When the substrate l,3-dien-8-yne was a terminal alkyne, the reaction provided an inter-molecular [2+2+2] product (Eq. 4.68). In water, a reactive cationic rhodium species was formed by the dissociation of the Rh-Cl bond in the presence of SDS. The SDS forms negatively charged micelles, which would concentrate the cationic rhodium species (Scheme 4.15). 

The rhodium-catalyzed intramolecular hydrosilylation of allylic alcohol derived silyl ethers has been described. Oxidative cleavage of the resulting cyclized hydrosilylation products affords a route to optically active diols (Scheme 28).129,130... 

Table 10 Impact of the chelating phosphine on levels of enantioselectivity in rhodium-catalyzed intramolecular hydrosilylation with [Rh(P-P)(acetone)2]+.

Hydroamination of olefins under most catalytic conditions proceed with Markovnikov addition of the N-H bond across the olefin. Shown below is a rhodium-catalyzed intramolecular, anti-Markovnikov, hydroamination developed for the synthesis of 3-arylpiperidines 167 <06JA6042>. Further evaluation of this reaction as a synthesis of multisubstituted piperidines revealed that substrates with substituents a or y to the amino group did not produce the expected piperidine, however, substrates with a substituent (1 to the amino group produce piperidines in high yield. 

A rhodium-catalyzed intramolecular C-H functionalization has been employed for the synthesis of bicyclic imidazoles. The alkene acts as an anchor to the metal, directing the C-H functionalization process, which involves the formation of an Rh(l) carbene intermediate (Equation (118)).107... 

Extensively developed by Ojima and co-workers, SiCaT and carbonylative silylcarbocyclization (CO-SiCaC) represent a rapid entry into polycyclic molecules of interest.271 For instance, the rhodium-catalyzed intramolecular SiCaT of triyne 441 afforded tricyclic compound 442 in high yield, accompanied by a small amount of cycloadduct 443 (Scheme 111).270... 

Angularly substituted bicyclo[4.3.0] systems can be synthesized efficiently through a rhodium-catalyzed intramolecular [4 + 2] diene-allene cycloaddition protocol (Scheme 16.74) [80]. 

Two years later, Bosnich described an extensive study of asymmetric rhodium-catalyzed intramolecular hydroacylation reactions [16]. Like Sakai, Bosnich found that Rh(l)/ BINAP is an unusually effective catalyst for this process, furnishing excellent enantioselectivity for a range of substrates (Eq. 13). Bosnich also reported thaL if the R substituent is a relatively unhindered alkyl (for example. Me) or an aromatic group, lower (< 80% ee) enantioselectivity is observed. 

It is possible to carry out the [2+2+2] cyclotrimerization reaction in a regioselective manner by using a partially or completely intramolecular approach. Rhodium-catalyzed intramolecular cyclotrimerization of 1,6,11-triynes, which construct fused 5-6-5 ring-systems, has been studied extensively [33-36]. Cyclization of 1,6,11-triyne 47 catalyzed by RhCl(PPh3)3, gives the tricyclic benzene 48 in good yield (Eq. 14) [33a]. 

This rhodium-catalyzed intramolecular cyclotrimerization method has been utilized as the key step for the synthesis of the marine illudalane sesquiterpenoid, alcyopterosin E, 51, which has a fused 5-6-5 ring system as illustrated in Scheme 7.15 [37]. 

Rhodium-catalyzed diazo insertions, known since 1976, have been extensively reviewed39. The first report40 indicated that rhodium acetate efficiently catalyzes diazo insertion into an alkene, giving the cyclopropane. Rhodium-catalyzed intramolecular C-H insertion was first observed by workers at Beecham Pharmaceuticals, who reported that 1, on exposure to a catalytic amount of rhodium acetate, cyclizes cleanly to the /1-lactam41. This approach to thienamycin derivatives has been developed further by these workers42,43. 

Chiral 3,3-disubstituted cyclopentanones. Taber et al have extended a synthesis of cyclopentanones by a rhodium catalyzed intramolecular C—H insertion (11,459) to a synthesis of (+ )-a-cuparenone (3), which contains a chiral quaternary center. Thus the chiral a-diazo-p-keto ester 1, prepared by alkylation of a chiral oxazolidone (11, 379-381) on treatment with Rh2(OAc)4 is converted into 2 in 67% yield. This product is converted in several steps into (+ )-3. 

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). 

Benzo[l, 2-c 3,4-c ]difurans (85) can be formed by the rhodium-catalyzed intramolecular [2 + 2 + 2]cycloaddition of some triynyl ethers (84) <88JCS(P1)1357>... 

Benzo[ ]furan-based diazobutenoates were used as a substrate to make a cyclopropane in 89% yield via a rhodium-catalyzed intramolecular process, as can be seen in Equation (74). Cyclopropane 88 was the key intermediate for the total synthesis of diazonamide A <20000L3521>. 

This report covers two topics (1) The generation of 2-thioxo-2,4-dihydro-3fT-imidazol-l-ium-l-imides as intermediates in the course of [3+2] cycloaddition reactions of azoalkenes and thiocyanic acid resulting in the formation of l-aminoimidazole-2-thione derivatives some further reactions of these heterocycles are presented as well. (2) The rhodium-catalyzed intramolecular interaction of co-diazenyl a -diazo ketones giving rise to the formation of mostly two cyclic azomethine imine isomers with an exocyclic terminal nitrogen atom and with all three... 

Benzimidazoles have been used as precursors to give other compounds. Microwave irradiation strongly accelerated the rhodium-catalyzed intramolecular coupling of benzimidazoles 113 C-H bond to pendant alkenes to afford tricyclic compounds 114, which are currently difficult to access by alternative methods <03OL2131>. Reaction of 2-aminoimidazole 115 with isatoic anhydride gave benzamide 116, which then reacted with orthoesters to provide benzimidazolyl quinazolinones 117 under microwave irradiation <03T4757>. 

Rhodium-catalyzed intramolecular reaction of diazo ketones like 175 leads mainly to carbenoid insertion into the a-C-H bond but a minor product is the 1,3-dioxolane (Equation 49) <1997JOC4910>. 

Rhodium-catalyzed intramolecular insertion into aromatic C—H bonds proceeds smoothly. - For instance, (113) cyclizes to a mixture of the heterocyclic product (114) and the carbacyciic product (115 equation 40). From the product ratios observed, one could conclude that the substituent on the aromatic ring can accelerate or decelerate C—H insertion. As with the results cited above (Section 4.2.3.4.3), the differences in reactivity observed can be ascribed to greater or lesser electron density in the target C—H bond. 

An elegant extension of this method is the tandem formation of two rings by rhodium catalyzed intramolecular addition of a diazo ketone to an enyne giving cyclopropene 3. ... 

Microwave irradiation has been shown to strongly accelerate the rhodium-catalyzed intramolecular C - H bond coupling of benzimidazole alkenes 99 to... 

Tan KL, Bergman RG, Ellman JA (2001) Annulation of alkenyl-substituted heterocycles via rhodium-catalyzed intramolecular C-H activated coupling reactions. J Am Chem Soc 123 ... 

Murakami s group has developed various rhodium-catalyzed C—C bond cleavages of small rings. Recently, they reported rhodium-catalyzed carbonylation reactions of spiropentanes involving two different types of C—C bond cleavage processes (Equation 11.43) [85]. The reaction allows for the synthesis of a series of 3-methylcyclopent-2-enones, one of which has been utilized as an intermediate in the concise synthesis of ( )- 3-cuparenone. Another example is the rhodium-catalyzed intramolecular olefin insertion of 3-(o-styryl)cyclobutanone to generate... 

Wender et al. demonstrated the rhodium-catalyzed intramolecular [6 + 2]-cycloaddition of 2-(l,6-dienyl)-cyclobutanones 158 (Scheme 55).130 The five-mem-bered heterocycles 159 were synthesized using substrates 158, which had a nitrogen or oxygen atom in a tether moiety. The reaction proceeds through formation of the five-membered metallacycle 160 and subsequent /Tcarbon elimination (de-carborhodation), leading to the nine-membered metallacycle 161, which produces 159 upon reductive elimination of Rh. 

The transition-metal-catalyzed reaction of diazo compounds 702, which have a N—H or O—H bond at an appropriate position, gives nitrogen- and oxygen-containing heterocycles 703 (Scheme 2 1 8).293 Wang and Zhu demonstrated a convenient synthesis of the polyfunctionalized /Tfluoropyrroles by the rhodium-catalyzed intramolecular N—H insertion reaction.2933 The reaction of d-amino-y,y-difluoro-a-diazo-/Tketo esters 704 in the presence of Rh2(OAc)4 gave the... 

This reaction type, in inter- and intramolecular versions, has been applied to the synthesis of numerous mono- and polyheterocyclic ring systems84. In some cases, remarkable stereoselectivities are achieved. Thus, rhodium-catalyzed intramolecular carbonyl ylide formation and [3 2] cycloaddition of l-diazoacety]-7,7-dimethylbicyclo[2.2.1]heptan-2-one (4) with N-... 

An insertion-reductive elimination sequence is involved in the rhodium-catalyzed, intramolecular hydroacylation of 4-alkenals to form cyclopentanes ... 

The 3+2 cycloreversion of the transient bicyclo[m.3.0]alkan-3-on-2-yl-l-oxonium ylide that was genenrated by the rhodium-catalyzed intramolecular reaction of a tetrahydrofuran substituted diazoketone was found to be stereospecific as illustrated below. The result supports a concerted mechanism <04JOCI331>. 

The mechanism proposed for the rhodium-catalyzed intramolecular insertion of carbenoids into C-H bonds adjacent to ethers [63] is more complex than previously recognized for such reactions. According to this mechanism (Scheme IV-32), the acetal product arises by oxygen-assisted hydride transfer to the electrophilic carbon of the carbenoid. 

Oshima et al. explored a cationic rhodium-catalyzed intramolecular [4+2] annulation of l,3-dien-8-ynes in water in the presence of sodium dodecyl sulfate (SDS), an anionic surfactant. When the substrate... 

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