Stereocontrol in Intermolecular Dirhodium(II)-Catalyzed Carbonyl Ylide Formation and Reactions. Dioxolanes and Dihydrofurans

Abstract

Ethyl diazoacetate undergoes dirhodium(II)-catalyzed reactions with aryl aldehydes to form 1,3-dioxolanes as mixtures of diastereoisomers in good yields. Carbonyl ylides are reaction intermediates. Catalyst dependent diastereocontrol is observed for reactions with p-nitrobenzaldehyde, but not for those with p-anisaldehyde or benzaldehyde, so that at least with transformations involving p-nitrobenzaldehyde a metal-stabilized ylide is responsible for product formation. Higher yields are obtained with catalysis by dirhodium(II) carboxamidates than with the carboxylates. Diastereoselectivity in 1,3-dioxolane formation that occurs through the "free" ylide can be effectively controlled so that only one diastereomer is produced through the use of 2,6-di-tert-butyl-4-methylphenyl diazoacetate (BDA) or dicyclohexylmethyl diazoacetate (DCM). The thermodynamically least stable all-cis trisubstituted 1,3-dioxolane is the primary product from p-nitrobenzaldehyde "cycloaddition" to the metal-stabilized ylide. Reactions that take place in the presence of p-anisaldehyde and dimethyl acetylenedicarboxylate (DMAD) result in the formation of one 2,5-dihydrofuran-2-carboxylate stereoisomer in good yield. In contrast, with p-nitrobenzaldehyde and DMAD both dihydrofuran stereoisomers are produced along with, mainly, the dioxolane derived from the metal-stabilized ylide; there is in this case competition between addition reactions of the "free" ylide and the metal-associated ylide.

Stereoselective Epoxide Generation with Cyclic Rhodium Carbenoids: A New Access to Spiro-indolooxiranes

“…The rhodium(II)-catalyzed decomposition of ethyl diazoacetate in the presence of aldehydes furnished dioxolanes (by means of 1,3-dipolar cycloaddition of the carbonyl ylide intermediate with a second equivalent of aldehyde) and did not produce oxiranes. 5 Despite the commonality and selectivity (vide infra) of rhodium(II) acetate catalyzed reactions of diazo carbonyl compounds, they were not found to produce the oxirane ring systems until the recent report by Doyle 6 and followed by Davies. 7 In an alternative route, Aggarwal delineated a useful method 8 for the formation of oxirane by intercepting the metal carbene with alkyl sulfide.…”

Tandem Cyclization‐Cycloaddition Reactions of Rhodium Generated Carbenoids from α‐Diazo Carbonyl Compounds.

“…Treatment of a composite of p-anisaldehyde and a catalytic amount of Rh 2 (OAc) 4 with ethyl diazoacetate resulted in the formation of two carbonyl ylide cycloaddition products, identified as 279 and 280, out of the four possible diastereomers in ,15% yield (Scheme 85). 123 Higher conversions were achieved with catalysis by dirhodium(II) caprolactamate, Rh 2 (cap) 4 (52%), but the same ratio of 279/ 280 did not change from 52:48. With p-nitrobenzaldehyde, all four isomers were obtained with different ratios of products based on the catalyst variations.…”

DFT investigation on mechanism of dirhodium tetracarboxylate-catalyzed O-H insertion of diazo compounds with H2O

“…An alcoholic oxonium ylide may react with other nucleophilic components such as aldehyde to form nucleophilic addition products [18][19][20][21][22][23], or perform a rapid 1,2-hydrogen shift reaction in the absence of nucleophilic components [14,15,18,19,24,25]. All these reactions can proceed directly through Rh(II) complexassociated oxonium ylides or through free oxonium ylides derived from Rh(II) complex-associated ylides via direct decomposition.…”

“…All these reactions can proceed directly through Rh(II) complexassociated oxonium ylides or through free oxonium ylides derived from Rh(II) complex-associated ylides via direct decomposition. Although oxonium ylide reactions with nucleophilic components were long believed to proceed through the free oxonium ylide [26][27][28], experimental evidence suggested that the nucleophilic addition of oxonium ylides generated by catalytic diazo compound decomposition proceed via Rh(II) complexassociated oxonium ylides instead of free oxonium ylides [18][19][20][21][22][23] …”