Formation of Tertiary Alcohols from the Rhodium-Catalyzed Reactions of Donor/Acceptor Carbenes with Esters

Abstract

Rhodium(II)-catalyzed reactions between isopropyl acetate and trichloroethyl aryldiazoacetates result in the formation of oxirane intermediates that ring open under the reaction conditions to form tertiary alcohols. When the reaction is catalyzed by the dirhodium tetrakis(triarylcyclopropanecarboxylate) complex, Rh( S-2-Cl,4-BrTPCP), the tertiary alcohols are formed with good asymmetric induction (80-88% ee).

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…The ylides of aldehydes and ketones are well explored on intermolecular reaction with carbenes. However, intermolecular reactions between carbenes and esters are uncommon, [33o] despite many examples of intramolecular ester ylide formation [33g–j,p] . Wang and co‐workers in 2020 developed a pioneering work on Huisgen cyclization/carbene cascade reaction with intermolecular trapping of the in situ carbene intermediate by esters resulted in Z ‐selectivity in many transformations.…”

“…Oxygen‐containing lewis bases such as ketones and ethers are generally converted into carbonyl ylides and oxonium ylides respectively with electrophilic carbenes [33h–n] . Cycloaddition/cyclization of highly reactive carbonyl yildes provided oxacycles or epoxides [33h–j,o] . Allyl‐substituted oxonium ylides on [2,3]‐sigmatropic rearrangements forms homoallyl ethers [33k,l] .…”

Spirocyclic Amide Acetal Synthesis by [CpRu]‐Catalyzed Condensations of α‐Diazo‐β‐Ketoesters with γ‐Lactams

“…Decomposition of diazo derivatives in the presence of Lewis bases is a recognized strategy to generate ylides efficiently [1–9] . With aldehydes and ketones, but also esters and amides, carbonyl ylides are formed, usually under light irradiation or metal‐catalyzed conditions ( Scheme 1, A ) [8,10–25] . These reactive intermediates condense to form epoxides ( A , path a ), act as 1,3‐dipoles in intra‐ and intermolecular cycloadditions ( A , path b ) or form enol ethers ( A , path c ) [26–30] .…”

Formation of β-Oxo-N-vinylimidates via Intermolecular Ester Incorporation in Huisgen Cyclization/Carbene Cascade Reactions

“…Electrophilic carbenes, often derived from diazo compounds like 1 (Scheme a), engage in ylide formation with oxygen-containing Lewis bases such as ketones (e.g., 2 ) and ethers (e.g., 5 ) to form carbonyl ylides 3 ,, and oxonium ylides 6 , − respectively. Highly reactive carbonyl yildes 3 can undergo cycloaddition or cyclization to build oxacycles 4a , or epoxides 4b . ,, Allyl-substituted oxonium ylides 6 can undergo [2,3]-sigmatropic rearrangements to form homoallyl ethers 7 . , Carbonyl ylide formation can be intermolecular or intramolecular. Intermolecular reactions between carbenes and ketones or aldehydes are well developed. − , However, intermolecular reactions between carbenes and esters are rare, despite many examples of intramolecular ester ylide formation. − , In fact, methyl benzoate was a stabilizing additive in rhodium-catalyzed cyclopropanation .…”

“…Highly reactive carbonyl yildes 3 can undergo cycloaddition or cyclization to build oxacycles 4a , or epoxides 4b . ,, Allyl-substituted oxonium ylides 6 can undergo [2,3]-sigmatropic rearrangements to form homoallyl ethers 7 . , Carbonyl ylide formation can be intermolecular or intramolecular. Intermolecular reactions between carbenes and ketones or aldehydes are well developed. − , However, intermolecular reactions between carbenes and esters are rare, despite many examples of intramolecular ester ylide formation. − , In fact, methyl benzoate was a stabilizing additive in rhodium-catalyzed cyclopropanation . A similar stabilizing interaction was seen in the cyclopropanation of carbene 8 (Scheme b) .…”