Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• ketones 42 [37]. With this transformation polysubstituted cyclohexanes 43 bearing four consecutive stereocenters are afforded through efficient one-pot cyclization with good yields (43–95%) and with high enantioselectivities (80–97% ee) (Scheme 15). In general, 1-azadienes 14 with different substitution

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• experimentally. In this work, we present our results on the computational study of the transannular reaction illustrated in Scheme 1 for several nonsymmetric tether combinations between the hydrazone and double bond moieties leading to a sort of condensed cyclohexanes (series a–f) and other bicyclic systems

• ), which are listed in Table 1. We used the phosphoric acid derived from 2,2'-biphenol as a model for the catalyst. The optimized geometries of the corresponding transition structures are given in Figure 1 (only those corresponding to fused cyclohexanes are shown, for the rest see Supporting Information

• cyclohexanes clearly showed that NCIs increase with the size of the tether (Figure 5) and the same effect is expected to account for the reagents. In general, a barrier could increase either by a destabilization of the transition structure or the stabilization of the reagents. In our case, the more stable is

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• context, 1,4-dithianes can thus also be considered as synthetic equivalents of cyclohexanes. Oxidative decoration of the carbon atoms in the dithiane ring can also be achieved via Pummerer-type chemistry, as illustrated by Pallumbo’s racemic synthesis of the dihydrodithiin-based nucleoside analog 135 via

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

• Sara Tejera,
• Giada Caniglia,
• Rosa L. Dorta,
• Andrea Favero,
• Javier González-Platas and
• Jesús T. Vázquez

Beilstein J. Org. Chem. 2019, 15, 2881–2888, doi:10.3762/bjoc.15.282

• /MeOH. The trans- and cis-1,2-di(triazol-1-yl)cyclohexanes 12 [14] and 14 (Scheme 4), respectively, were prepared from 1-bromo-4-ethynylbenzene and their corresponding diazides, 11 and 13, through CuAAC reactions [16][17][18]. As can be seen in Figure 1 and Table 1, all these compounds except 9 (having

• -triazol-1-yl)cyclohexanes 12 and 14, having the same configuration as compounds 7f and 8f, respectively, were analyzed. Both compounds formed gels, but the trans stereoisomer 12 did so only at a low temperature (8 °C) in DMSO (G = 1.1, w/w), similar to the β-anomer 7f, which possessed the same trans

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• Abstract The presence of strong stereoelectronic interactions involving the substituents in cis-2-substituted cyclohexanes may lead to results different from those expected. In this work, we studied the conformational behavior of cis-2-fluoro- (F), cis-2-chloro- (Cl), cis-2-bromo- (Br) and cis-2

• analysis; Introduction cis-2-Substituted cyclohexanes are interesting from the conformational point of view, since one of the substituents should be axial. Generally, bulky substituents prefer the equatorial position to avoid steric repulsions [1]. Nevertheless, two distinct groups may provoke a

• electron-density acceptors, and their presence in a system suggests the possibility of these interactions [17][21]. Although there have been several works on the conformational preference of 1,2-disubstituted cyclohexanes [4][11][12][13][14][20][22][23][24][25][26][27][28][29], cis-2-halocyclohexylamines

Gram-scale preparation of negative-type liquid crystals with a CF₂CF₂-carbocycle unit via an improved short-step synthetic protocol

• Tatsuya Kumon,
• Shohei Hashishita,
• Takumi Kida,
• Shigeyuki Yamada,
• Takashi Ishihara and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 148–154, doi:10.3762/bjoc.14.10

• cyclohexanes containing the CF2CF2 fragment, e.g., 2b and 2c, were also obtained as a mixture of trans/cis diastereomers, but careful recrystallization enabled the isolation of the trans isomers in a pure form. A noteworthy advantage of the current synthetic protocol is that starting from the commercially

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• ; fluorinated cyclohexanes; Introduction The all-cis-2,3,5,6-tetrafluorocyclohexane 1 ring has been introduced recently as a polarized cyclohexane ring and it has been a focus of our research group to elaborate new building blocks that enable the introduction of this motif into organic discovery programmes

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• interaction of the positive non-fluorous face with the π-system of an aromatic ring by single crystal X-ray diffraction and NMR experiments. Additionally, the polarity of 4c has been calculated by computational optimisations. It follows that functionalised cyclohexanes containing the 1,3-di-CF2 motif would

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• and co-workers disclosed an elegant synthesis of polysubstituted cyclohexanes, utilizing the chiral adduct 107 of the Michael reaction of chalcone 109 catalyzed by a bifunctional thiourea 56 [54]. The authors used a range of different adducts, as well as monosubstituted and disubstituted α,β

• , Enders and co-workers described the three-component domino Michael–Michael aldol reaction between β-ketoesters 153, nitroalkenes 77 and α,β-unsaturated aldehydes 154, producing heavily substituted cyclohexanes 155 containing six contiguous stereocenters with excellent stereocontrol (Scheme 49) [70]. In

• Henry–Michael–retro-Henry–Henry domino cascade to furnish substituted cyclohexanes with three adjacent stereocenters [84]. A wide range of aldehydes 196 were tested, obtaining the desired products 197 in good yields and good stereoselectivities (Scheme 63). The process follows an interesting mechanism

Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane

• Mohammed Salah Ayoup,
• David B. Cordes,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 2671–2676, doi:10.3762/bjoc.11.287

• conformation, they always have two 1,3-diaxial C–F bonds on one face of the ring, and this results in ring systems also with large dipole moments (4.9 D for 2 and 5.2 D for 3). The nature of these cyclohexanes, where the two faces are oppositely polarised, presents a unique property for use in pharmaceuticals

Organocatalytic and enantioselective Michael reaction between α-nitroesters and nitroalkenes. Syn/anti-selectivity control using catalysts with the same absolute backbone chirality

• Jose I. Martínez,
• Uxue Uria,
• Maria Muñiz,
• Efraím Reyes,
• Luisa Carrillo and
• Jose L. Vicario

Beilstein J. Org. Chem. 2015, 11, 2577–2583, doi:10.3762/bjoc.11.277

• ][25][26]. In this context, we have recently reported a catalytic and enantioselective Michael/Michael cascade reaction in which α-nitro-δ-ketoesters react with nitroalkenes to provide densely functionalized cyclohexanes in excellent yield and stereoselectivity (Scheme 1) [27]. This reaction made use

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• to imines (Scheme 2) [41][42]. The mechanism was believed to involve e– capture by the imine thereby forming α-aminodiphenylmethyl radicals that underwent hetero-coupling with the allyl radicals generated from the allylic C–H containing substrates. Cyclohexanes, dihydrofurans, cyclopentenes and α

Synthesis of 2,3-dihydronaphtho[2,3-d][1,3]thiazole-4,9-diones and 2,3-dihydroanthra[2,3-d][1,3]thiazole-4,11-diones and novel ring contraction and fusion reaction of 3H-spiro[1,3-thiazole-2,1'-cyclohexanes] into 2,3,4,5-tetrahydro-1H-carbazole-6,11-diones

• Lidia S. Konstantinova,
• Kirill A. Lysov,
• Ljudmila I. Souvorova and
• Oleg A. Rakitin

Beilstein J. Org. Chem. 2013, 9, 577–584, doi:10.3762/bjoc.9.62

• reaction of anthracene-1,4-diones 4 led unexpectedly to the corresponding 2-thioxo-2,3-dihydroanthra[2,3-d][1,3]thiazole-4,11-diones 10. The reaction of 3H-spiro[1,3-thiazole-2,1'-cyclohexanes] 1d, 2d with Et3N in chlorobenzene under reflux yielded 2,3,4,5-tetrahydro-1H-carbazole-6,11-diones 15, 16, i.e

• (thiazol-2,1'-cyclohexanes) to tetrahydroindoles has been so far unknown, similar dehydration of spirooxazolocyclohexane to tetrahydroindoles by treatment with base has been previously described [21][22]. Conclusion The reaction of N-substituted 2-(methylamino)naphthoquinones and -anthracene-1,4-diones

• -ethyldiisopropylamine in the reaction of 2-(methylamino)anthracene-1,4-diones with sulfur monochloride was discovered and explained. 3H-Spiro(thiazol-2,1'-cyclohexanes) underwent a new ring contraction and fusion reaction resulting in the formation of tetrahydroindoles. Experimental Melting points were determined on a

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• -(hydroxythiophene-2-yl-methyl)-[1,3]dithiole-2-thione (A) [29] A solution of 1,3-dithiole-2-thione (4.00 g, 29.8 mmol) in dry tetrahydrofuran (250 mL) was cooled to −78 °C under dry nitrogen. Lithium diisopropylamide mono(tetrahydrofuran) (1.5 M in cyclohexanes, 21.9 mL, 32.9 mmol) was added and the mixture was

• stirred for 20 minutes after which time thiophene-2-carboxaldehyde (3.1 mL, 32.9 mmol) was added and the mixture stirred for a further 10 min. Another portion of lithium diisopropylamide mono(tetrahydrofuran) (1.5 M in cyclohexanes, 21.9 mL, 32.9 mmol) was added and the mixture was stirred for 15 min

Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

• Rajeev K. Shrivastava,
• Elise Maudru,
• Gurdial Singh,
• Richard H. Wightman and
• Keith M. Morgan

Beilstein J. Org. Chem. 2008, 4, No. 43, doi:10.3762/bjoc.4.43

• gave mixtures of syn- and anti-alkynols 2a–2c which were separated following protection as methoxymethyl ethers. These were converted to the corresponding iodides which underwent 6-exo-dig radical cyclisation to afford chiral cyclohexanes and carbasugars. Oxidation of the primary alcohols 6a–b gave the

• corresponding aldehydes which on treatment with Grignard reagents afforded a mixture of alcohols. The corresponding iodides underwent similar 6-exo-dig cyclisation to give fully functionalised cyclohexanes. Keywords: carbasugars; cyclisation; cyclohexanes; 6-membered ring; stereoisomers; Introduction The use

• closure of a radical onto an alkyne [14]. In contrast there are fewer reports of the corresponding 6-exo-dig cyclisation to prepare fully functionalised cyclohexanes and carbasugars. The reason for this may be inferred from the observation that the formation of six-membered rings by a radical ring closure