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Carbenoid rhodium, from diazo carbonyl

The interception of the transient rhodium carbenoid formed from diazo compound 601 by a carbonyl oxygen produces carbonyl ylides that, upon dimerization and subsequent rearrangement, give 56% of compound 602 (92JA593),... [Pg.190]

Doyle et al. (34) were the first group to generate isomiinchnones from diazo imides using Rh(II) catalysis. For example, isomiinchnone 60 was produced from diazo imide 59, but attempts to trap this species with ethyl acrylate were unsuccessful. The only material identified was the isomiinchnone hydrolysis product. This use of Rh(II) to generate a rhodium-carbenoid species from an a-diazo carbonyl compound is reminiscent of the first successful synthesis of... [Pg.689]

Addition of carbenoids derived from a-diazo carbonyl compounds to prostereogenic olefins can furnish two diastereomeric cyclopropane derivatives (dsjtrans- or euefo/exo-isomers). The metal-catalyzed transfer of alkoxycarbonyl carbenes has been closely investigated it usually furnishes the mwv-substituted cyclopropanes with moderate to good preference. The rhodium(II/-catalyzed reaction of ethyl diazoacetate with various olefins typically demonstrates that the d.r. (trans/cis) increases when the substituent on the olefin becomes sterically more demanding5. [Pg.1018]

A type of 1,3-dipole that has received considerable recent interest is the carbonyl ylide. One method for its formation makes use of carbenoid chemistry (see Section 4.2). Cyclization of an electrophiUc rhodium carbenoid onto a nearby carbonyl group provides access to the carbonyl ylide. Cycloaddition with an alkyne or alkene dipolarophile then gives the dihydro- or tetrahydrofuran product. For example, the carbonyl ylide 235, formed from the diazo compound 234 and rhodium(II) acetate, reacts with dimethyl acetylenedicarboxylate to give the bridged dihydrofuran 236 (3.148). [Pg.230]

After copper and palladium, rhodium is the third most important transition metal for the synthesis of the indole ring. For a 2007 review on this reaction, see Patil and Paiil [1], Some early examples (Scheme 1) are Alper s rhodium reaction of 2-aryl-2/7-azirines to give 2-styiylindoles (equation 1) [2], Watanabe s Rh-catalyzed Fischer indole synthesis (equation 2) [3], Ucciani s 3-methylindole synthesis via the hydroformylation of o-nitrostyrene (equation 3) [4], and Burst s preparation of 3-acetyl-2-hydrox-yindoles from the Rh-catalyzed decomposition and carbenoid aromatic C-H bond insertion (equation 4) [5]. Narasaka extended Alper s 2-aryl-2//-azirine reaction to a Rh(II)-catalyzed synthesis of 2,3-disubstituted indoles [6], and both Cenini [7] and Alper [8] stretched the deoxygenation of o-nitrostyrenes to give indoles. Burst s Rh-catalyzed decomposition of a-diazo carbonyl compounds was used by Bauban [9] and Jha [10] in the synthesis of substituted oxindoles. [Pg.632]


See other pages where Carbenoid rhodium, from diazo carbonyl is mentioned: [Pg.152]    [Pg.411]    [Pg.436]    [Pg.729]    [Pg.21]    [Pg.32]    [Pg.206]    [Pg.554]    [Pg.83]    [Pg.362]    [Pg.480]    [Pg.519]    [Pg.443]    [Pg.1576]    [Pg.124]    [Pg.150]    [Pg.223]    [Pg.309]    [Pg.166]    [Pg.1576]    [Pg.223]    [Pg.325]   
See also in sourсe #XX -- [ Pg.1057 ]

See also in sourсe #XX -- [ Pg.1057 ]

See also in sourсe #XX -- [ Pg.1007 ]




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Rhodium carbonyls

Rhodium, from diazo carbonyl

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