Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• last step involves the enamine intermediate which drives an intramolecular aldol condensation to form the final product 5. In this elegant cascade process, catalyst 1 promotes three consecutive carbon–carbon bond forming steps generating four stereogenic centers with high diastereoselectivity and

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• aldol reaction is one of the most powerful tools to achieve this transformation [1][2][3][4][5][6][7][8]. In particular, the intramolecular aldol condensation is an important approach to the formation of ring systems such as cyclic β-hydroxy carbonyl products or cyclic α,β-unsaturated carbonyl products

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• Michael addition with another molecule of 3-phenacylidieneoxindole to yield intermediate B. Finally, an intramolecular aldol condensation takes place between the carbanion and the carbonyl group of intermediate B towards the formation of the dispirocyclopentanebisoxindole derivative. To support the

• cyclization of two molecules of 3-phenacylideneoxindoles. In this reaction tosylhydrazine serves as reducing agent to reduce one molecule of 3-phenacylideneoxindole to 3-phenacylindolinone which, under base-catalyzed conditions, involves a sequential Michael addition/intramolecular aldol condensation with

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• later stage of the synthesis without the need of pre-installation of necessary functional groups as a reaction precursor, for instance, ring-closing metathesis, intramolecular aldol condensation, and others. One major issue that still needs to be addressed is the selectivity of the all carbon [3 + 2

Synthetic terpenoids in the world of fragrances: Iso E Super^® is the showcase

• Alexey Stepanyuk and
• Andreas Kirschning

Beilstein J. Org. Chem. 2019, 15, 2590–2602, doi:10.3762/bjoc.15.252

• ]. Oxidation, iodocarboxylation and elimination yielded the lactone 43. A series of functional group manipulations provided enone 44, which underwent a cuprate-mediated Michael addition and liberation of the aldehyde 46 upon ozonolysis. After intramolecular aldol condensation the resulting enone 47 was

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• ,S-acetals 9a–c since the X-ray crystal structure of Meldrum’s acid-based N,S-acetal was reported by Wentrup [84]. In addition, the intramolecular aldol condensation of Meldrum’s acids did not occur due to the ketone structures. Table 2 displays the 1H NMR result of the sulfur ylide-like intermediate

• methanimidothioate 7ao, and time dependent experiments of the intramolecular aldol condensation of N,S-acetal 7aa to 8aa in N,N-dimethylformamide-d7 at room temperature confirmed the formation of the stable sulfur ylide-like intermediates, thus indicating the successful transformation into thiophenes 8an, 8ao, and

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• hydrolysis of the oximino group gave target steroid 25 with the desired configuration of all stereogenic centers. In the attempted route to (+/−)-isocomene, Oppolzer and co-workers suggested pentalenone 29, accessible by an intramolecular aldol condensation/elimination of diketone 30, as a key precursor

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

• Felicia D’Andrea,
• Giorgio Catelani,
• Lorenzo Guazzelli and
• Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

• ; intramolecular aldol condensation; stereoselective hydride reduction; Introduction Inositols are a family of biologically relevant compounds [1][2] constituted by nine stereoisomeric hexahydroxycyclohexanes (Figure 1): five have been found in nature (myo, scyllo, D-chiro, L-chiro, and neo), while the remaining

• intramolecular aldol condensation was also performed on aldohexos-5-uloses of the L-lyxo and D-xylo series bearing a methyl protection on position 4 or a benzyl protection on position 3 (compounds 4 [35] and 10 [38], respectively). The stereo-outcome and the yields confirmed the cyclisation results obtained for

• dibenzyl derivatives. Considering the results obtained, the intramolecular aldol condensation of the lyxo and arabino stereoseries affords the inososes in fairly good yields (54–60%) [33][34][35], while the same reaction run on the ribo and xylo stereoseries gives the cyclization products only in moderate

Synthesis and bioactivity of analogues of the marine antibiotic tropodithietic acid

• Patrick Rabe,
• Tim A. Klapschinski,
• Nelson L. Brock,
• Christian A. Citron,
• Paul D’Alvise,
• Lone Gram and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2014, 10, 1796–1801, doi:10.3762/bjoc.10.188

• . Oxidative cleavage of the glycol with NaIO4 resulted in a β-ketoester aldehyde that upon treatment with silica gel underwent an intramolecular aldol condensation to a mixture of 10a and 11a that were separable by column chromatography. Oxidation with DDQ gave tert-butyl tropone-2-carboxylate (12a) that was

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• ) units. The remaining methyl groups are believed to be installed by S-adenosyl methionine (SAM). An intramolecular Aldol condensation generates the pyrrolinone 62, which reacts via an [4 + 2]-cycloaddition to prochaetoglobosin I (63) [56]. Recently, gene disruption studies of Chaetomium globosum revealed

•  12) using a dimethylformamide acetal-mediated cyclodehydration of 105. The isoindole unit of 105 was prepared from the condensation of 103 and 104. Oxygen–sulfur exchange provided the thiophthalimide 105, which could be converted to magallanesine (97) via an intramolecular aldol condensation in one

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• upon intramolecular aldol condensation [25][26][27]. Subsequently, the aldehyde 15 was reduced to the allylic alcohol 19 with LiAlH4 and converted into the acetate 20 [28]. Hydroboration of 20 using disiamylborane proceeded with high stereoselectivity affording 16 as a single stereoisomer [17][28

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• and the final product 4. The isolated intermediate 5 could be transformed into a mixture of 6 and 4 under the reaction conditions, finally yielding 4 via intramolecular aldol condensation. This gold-catalyzed cyclization of alkynyl ketones to enones was successfully utilized in a cascade reaction by

• before being transformed into the final product via intramolecular aldol condensation. Fiksdahl and co-workers investigated a similar gold-catalyzed transformation of internal 1,6-diynes 18 in methanol at room temperature (Scheme 14) [50][51]. Interestingly, a non-conjugated five-membered cyclic enone 19