- Synthetic application of sequential palladium-catalyzed allylic acetate alkylation and michael addition carbocyclization: Synthesis of (±)-dihydroerythramine
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A new synthetic route to aromatic Erythrina alkaloids is reported. (Nitromethyl)arene 3 underwent a palladium-catalyzed annulation reaction with allylic acetate 11 to provide nitro esters 12a and 12b by an (η3-allyl)palladium complex alkylation/Michael addition domino sequence. Reduction of the nitro group of 12a, followed by cyclization of the resulting amino group on the acetate appendage, afforded the bicyclic lactam 29. Two-carbon elongation at the nitrogen atom of 29 by hetero Michael addition of vinyl phenyl sulfoxide, followed by Pummerer-type cyclization, gave cis-11-phenylthioerythrinan-8-one (32a, 32b) along with the rearranged lactam 34. Reductive desulfurization at C-11, and oxidative cleavage of the C-3 exocyclic double bond afforded the 15,16-(methylenedioxy)erythrinan-3,8-dione (42). Reduction of the C-3 carbonyl group and methylation of the resulting alcohol afforded hexahydrocrystamidine (44), which was further reduced by aluminum hydride to give (±)-dihydroerythramine (9).
- Jousse-Karinthi, Celine,Riche, Claude,Chiaroni, Angele,Desmaele, Didier
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- Alkylation of CH acids with haloidalkyl-1,3-dioxolanes
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Alkylation of diethyl malonate and Meldrum acid with haloalkyl-1,3-dioxolanes has afforded the substituted malonates; their decarboxylation has led to the formation of esters containing a cycloacetal fragment. Reactions of the substituted malonates with urea have yielded the corresponding substituted barbiturates. Monodecarboxylation of the obtained malonates has led to the formation of 1,3-dioxolane-carboxylates.
- Raskil’dina,Borisova, Yu. G.,Spirikhin,Zlotsky
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- The six-membered annulation reaction involving sequential palladium-catalyzed allylic alkylation and Michael addition: Scope and limitations
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The palladium-catalyzed condensation of a variety of active methylene compounds with methyl 6-acetoxymethyl-hepta-2,6-dienoate was investigated. The six-membered adducts resulting from a η3 palladium complex alkylation-Michael addition sequence were obtained with moderate to good yields. In some cases, further evolution of the primary adduct was observed. The process has been expanded to access nitrogen heterocycles by using sodium p-toluenesulfonamide as the nucleophilic partner.
- Jousse-Karinthi, Céline,Zouhiri, Fatima,Mahuteau, Jacqueline,Desma?le, Didier
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- Practical Synthesis of Phosphinic Dipeptides by Tandem Esterification of Aminophosphinic and Acrylic Acids under Silylating Conditions
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In this report, a synthetic protocol for the preparation of phosphinic dipeptides of type 5 is presented. These compounds serve as valuable building blocks for the development of highly potent phosphinopeptidic inhibitors of medicinally relevant Zn-metalloproteases and aspartyl proteases. The proposed method is based on the tandem esterification of α-aminophosphinic and acrylic acids under silylating conditions in order to subsequently participate in a P-Michael reaction. The scope of the transformation was investigated by using a diverse set of readily available acrylic acids and (R)-α-aminophosphinic acids, and high yields were achieved in all cases. In most examples reported herein, the isolation of biologically relevant (R,S)-diastereoisomers became possible by simple crystallization from the crude products, thus enhancing the operational simplicity of the proposed method. Finally, functional groups corresponding to acidic or basic natural amino acids are also compatible with the reaction conditions. Based on the above, we expect that the practicality of the proposed protocol will facilitate the discovery of pharmacologically useful bioactive phosphinic peptides.
- Kokkala, Paraskevi,Voreakos, Kostas,Lelis, Angelos,Patiniotis, Konstantinos,Skoulikas, Nikolaos,Devel, Laurent,Ziotopoulou, Angeliki,Kaloumenou, Eleni,Georgiadis, Dimitris
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supporting information
(2022/02/21)
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- Iron-Catalyzed Tertiary Alkylation of Terminal Alkynes with 1,3-Diesters via a Functionalized Alkyl Radical
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Direct oxidative C(sp)?H/C(sp3)?H cross-coupling offers an ideal and environmentally benign protocol for C(sp)?C(sp3) bond formations. As such, reactivity and site-selectivity with respect to C(sp3)?H bond cleavage have remained a persistent challenge. Herein is reported a simple method for iron-catalyzed/silver-mediated tertiary alkylation of terminal alkynes with readily available and versatile 1,3-dicarbonyl compounds. The reaction is suitable for an array of substrates and proceeds in a highly selective manner even employing alkanes containing other tertiary, benzylic, and C(sp3)?H bonds alpha to heteroatoms. Elaboration of the products enables the synthesis of a series of versatile building blocks. Control experiments implicate the in situ generation of a tertiary carbon-centered radical species.
- Tian, Ming-Qing,Shen, Zhen-Yao,Zhao, Xuefei,Walsh, Patrick J.,Hu, Xu-Hong
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supporting information
p. 9706 - 9711
(2021/03/19)
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- Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate
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We have explored here the scope of the age-old diethyl malonate-based accesses to α-amino esters involving Knoevenagel condensations of diethyl malonate on aldehydes, reductions of the resulting alkylidenemalonates, the preparation of the corresponding α-hydroxyimino esters and their final reduction. This synthetic pathway turned out to be general although some unexpected limitations were encountered. The synthetic modifications of some of the intermediates - using Suzuki-Miyaura coupling or cycloadditions - before undertaking the oximation step - provided accesses to further α-amino esters. Moreover, other pathways to α-hydroxyimino esters were explored including an attempt to improve the cycloadditions between ethyl β-bromo-α-hydroxyiminocarboxylate and various alkylfuranes.
- Coutant, Eloi P.,Hervin, Vincent,Gagnot, Glwadys,Ford, Candice,Baatallah, Racha,Janin, Yves L.
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supporting information
p. 2853 - 2860
(2018/11/26)
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- Organocatalyzed Tsuji-Trost reaction: a new method for the closure of five- and six-membered rings
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A combination of organotransition metal catalysis and organocatalysis allows for Tsuji-Trost 5-exo- and 6-exo-cyclizations of aldehydes. This transformation can also be accomplished as a catalytic asymmetric reaction, which affords vinylcyclopentane deriv
- Vulovic, Bojan,Bihelovic, Filip,Matovic, Radomir,Saicic, Radomir N.
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scheme or table
p. 10485 - 10494
(2010/02/28)
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- Synthetic studies on azadirachtin: Asymmetric synthesis of the tetracyclic decalin part of azadirachtin
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A synthesis of the tetracyclic decalin part of azadirachtin in the naturally occurring form is described. The key reactions involve the Corey-Bakshi-Shibata (CBS) asymmetric reduction of the ketone, and an intramolecular Diels-Alder (IMDA) reaction.
- Kanoh,Ishihara,Yamamoto,Murai
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p. 1878 - 1893
(2007/10/03)
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- Synthetic studies on spiroketal natural products. IV. A stereoselective synthesis of (3S,5S,6R,9R,R(S))-3-benzyloxymethyl-9-hydroxymethyl-5-(p-tolyl)sulfin yl-1,7-dioxaspiro[5.5]undecane, a key intermediate for talaromycins
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A dioxaspiro compound (4), a common intermediate for the synthesis of talaromycin A (1) and (-)-talaromycin B (2), was synthesized by two routes utilizing two kinds of asymmetric recognition of prochiral 1,3-diols controlled by sulfinyl chirality, that is, firstly by acid promoted diastereoselective C-O bond fission of the bicyclic acetal (7) to give the dihydropyran derivative (6), which has an S-hydroxymethyl group at the C3-position (7 → 6), and secondly by diastereoselective intramolecular Michael addition of the diol (5), in which the three chiral centers at C5, C6, C9 were constructed in one step (5 → 4).
- Iwata,Maezaki,Hattori,Fujita,Moritani,Takemoto,Tanaka,Imanishi
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p. 339 - 345
(2007/10/02)
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- Synthesis of 2-Alkyl-6-aza-8-oxabicyclooctanes
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Synthesis of 2-alkyl-6-aza-8-oxabicyclooctanes via an aminoalcohol acetal intermediate is described.
- Reddy, C. P.,Rao, R. Balaji
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p. 367 - 368
(2007/10/02)
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