Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Cyclic 2-alkoxycarbonyl synthesis

Addition to cyclic iminium salts has been utilized in alkaloid synthesis. A zinc-promoted reductive coupling reaction of iminium salts and alkyl halides has been reported by Shono et al. (Scheme 8). Evidence delineating the mechanistic course (organozinc addition or electron transfer reaction) of the addition has not been established. In contrast to organolithium or Grignard additions, aromatic halogen and alkoxycarbonyl substituents are compatible with this methodology. The intramolecular version of this reaction has been employed for the synthesis of tricyclic amines (53 equation 9). [Pg.366]

Unquestionably, one of the most attractive synthetic methods for the preparation of dialkyl 2-(alkoxycarbonyl)ethylphosphonates involves the conjugate addition of a dialkyl phosphite to the carbon-carbon double bond of a,p-unsaturated carboxylates (Pudovik reaction, Scheme 8.44). In the presence of EtONa, diethyl phosphite reacts vigorously with acrylate in EtOH to give the Michael addition product in 84% yield. The reaction is applied with success to the synthesis of dialkyl 2-(alkoxycarbonyl)ethylphosphonates bearing a large variety of acyclic (symmetric - or disymmetric 30 or cyclic (symmetric or disynunetric ) substituents at phosphorus. [Pg.445]

By this point, we felt that we had expended enough effort on model reactions. We had established that cyclic aldehydes containing an a-tertiary center were suitable substrates with the 2-alkoxycarbonyl 3-substituted allylboro-nates. This realization provided enough assurance to undertake the total synthesis with optimism. [Pg.95]

Hydroformylation of substrates incorporating O- or N-nudeophilic moieties leads to cyclic hemiacetals, acetals, 0,N-acetals, or enamines depending on the reaction conditions and the functional groups of the substrates. In the total synthesis of the anticancer agent, natural product leucascandroUde A (24), three different carbonyla-tion steps were incorporated (Scheme 12.1). Alkene 20 underwent a cyclohydrocar-bonylation reaction under hydroformylation conditions, resulting in the formation of hemiacetal 21. The other two carbonylation steps involved formylation of 18 and intramolecular alkoxycarbonylation of alkene 22 [28]. Various tryptamine derivatives [29] and the framework of piperidine alkaloids [30] were also synthesized via cyclohydrocarbonylation starting from functionalized homoallylic amines or aniline derivatives, respectively. [Pg.305]

Lactone synthesis through the reaction of 2-(alkoxycarbonyl)allyl metal species to carbonyl substrates holds a main position for the synthesis of the a-methylene derivatives. In 2(X)5, Hall et al. [30] obtained an interesting result in a TfOH-catalyzed reaction of a benzaldehyde derivative bearing electronically rich arene structure with (E)-crotyl boron reagent (E)-39 (Scheme 16). In this case, if the reaction proceeds via normal cyclic six-membered transition... [Pg.263]

A 1968 patent report has been developed into a practical synthesis of /S-keto-esters by Lewis acid-catalysed condensations of alkyl nitriles with acetoacetates and subsequent acid hydrolysis (Scheme 34). " A new three-step procedure for the alkoxycarbonylation of cyclic ketones consists of an addition of... [Pg.107]


See other pages where Cyclic 2-alkoxycarbonyl synthesis is mentioned: [Pg.8]    [Pg.206]    [Pg.207]    [Pg.801]    [Pg.1821]    [Pg.281]    [Pg.220]   
See also in sourсe #XX -- [ Pg.2 , Pg.806 ]




SEARCH



Alkoxycarbonyl

Alkoxycarbonylation

Cyclic 2-alkoxycarbonyl

Cyclic synthesis

© 2024 chempedia.info