Rhodium indanones

The oxime nitrogen lone pair of electrons must be properly oriented so as to interact with the rhodium carbenoid.84 Thus, subjection of the -oximino isomer 182 to a catalytic quantity of Rh2(OAc)4 in CH2C12 (40 °C) with a slight excess of DMAD afforded the bimolecular cycloadduct 184 in 93% yield. In sharp contrast, when the isomeric Z-oximino diazo derivative 183 was exposed to the same reaction conditions, only indanone-oxime 185 (80%) was obtained. The formation of this product is most likely the result of an intramolecular C-H insertion reaction. 

A bicyclic ketone was generated when 1,2-diphenylethyne was heated with CO, methanol and a dirhodium catalyst. " 2-Iodostyrene reacted at 100°C with CO and a palladium catalyst to give the bicyclic ketone l-indanone. " ° Another variation reacted a conjugated allene-alkene with 5 atm of CO and a rhodium catalyst to give a bicyclic ketone.An intermolecular version of this reaction is known... 

The extent to which secondary and tertiary amines are formed by reductive alkylation is controlled to some degree by the steric bulk of the amine and the carbonyl compound. The more hindered the system, the higher the temperature and hydrogen pressure needed to affect the reaction. While the reductive alkylation of secondary aliphatic amines with formaldehyde takes place under mild conditions (Eqn.l9.52X N,N-dimethylaniline was prepared by reductive alkylation over palladium at 120°C and 15 atmospheres pressure (Eqn. 19.53). 153 54 Reductive alkylation of aniline with acetone over palladium gave a 67% yield of the monoalkylaniline at 100°C and 40 atmospheres pressure but secondary amine formation using the more sterically accessible ketones, 2-tetralone or 2-indanone, took place at room temperature and 4 atmospheres pressure (Eqn. 19.54). 55 Palladium was the preferred catalyst in these reactions since with platinum or rhodium ring hydrogenation was also observed. 54,155... 

A few examples of vinylic to aryl rhodium migration have also been observed. One such example was discovered independently by two groups almost at the same time [77,78], In this reaction, aryl propargyl alcohols undergo a rhodium-catalyzed isomerization to furnish indanone products (Table 12). The reaction proceeds by a fairly complicated mechanism shown in Scheme 19. Thus, after base-promoted ligand... 

In 2006, the group of Artok showed that 5-aryl-2(5H)-furanones could be prepared in moderate to good yields by a rhodium-catalyzed carbonylative arylation of internal alkynes with aryl boronic acids (Scheme 1.9a) [22]. a,P-Unsaturated ketones (chal-cone derivatives) were formed as the major product when some TFA (trifluoroacetic acid) was added under the same reaction conditions [23a]. By varying the catalytic system, indanones could be produced as the main product [23b]. The chemical behavior of terminal alkynes is different, and either a,P-unsaturated ketones or furans starting from propargylic alcohols can be achieved (Scheme 1.9b) [24, 25]. In the case of vinyl ketones, 1,4-diketones were obtained by rhodium-catalyzed coupling of arylboronic acids in the presence of 20-40 bar of CO [26]. In 2007, Chatani demonstrated that indenones could be accessed by a carbonylative rhodium-catalyzed cyclization of alkynes with 2-bromophenylboronic adds (Scheme 1.9c) [27]. Here, the key intermediate is a vinylrhodium(I) spedes that is formed by transmetaUation of RhCl with 2-bromophenylboronic acid followed by insertion of... 

Scheme 8.45 Rhodium-catalyzed asymmetric synthesis of 3,3-disubstituted 1-indanones 161.

Alkenyl-l-alkynylcyclopropane 33 underwent rhodium-catalyzed tandem Pauson-Khand reaction/spiropentane carbonylation to give 6-hydroxy-l-indanone 34 (Scheme 2.30) [46]. 

Asymmetric ring-opening reorganization of cyclobutanol 42 proceeded via 1,4-rhodium migration to give 1-indanone 43 in a diastereo- and enantioselective manner (Scheme 3.24) [35]. 

Murakami et al. reported the total synthesis of (-)-(/ )-herbertenol via construction of the sterically-congested quaternary stereocenter by enantioselective C-C bond cleavage (Scheme 8.7) [26]. The symmetrical cyclobutanone 39 was prepared from 2-bromo-5-methylbenzaldehyde (38). Treatment of 39 with a catalytic amount of a rhodium(I)/SEGPHOS (5,5 -bis(diphenylphosphino)-4,4 -bi-l,3-benzodioxole) complex induced enantioselective cleavage of the prochiral C-C bond to produce indanone 40. Mechanistically, transmetalation of the boryl... 

Furthermore, this strategy was applied successfully in the enantioselective synthesis of alcyopterosin I (28), which has a 6-6-5 ring system, as well as for the bicyclic alcyopterosins N (30) and C (31) (Scheme 7.7) [12], The latter became available through a selective ring opening of the ether tether in 28 to provide the indanone 29. Notably, the efficiency of the synthetic sequences leading to the alcyopterosins is not only the result of a powerful rhodium-catalyzed intramolecular [2 + 2 -f 2]... 

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