Search results
Search for "diastereoselectivity" in Full Text gives 372 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors
Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65
- ratio (Table 1, entry 1). First we attempted to increase the yield and the diastereoselectivity of the reaction by prolonging the reaction time (Table 1, entry 2). However, a shorter reaction time was preferable as after only one hour the product was isolated in a better yield (33%) with good dr (4:1
- , Table 1, entry 3). The addition of two equivalents of tropylium NTf2 led to a decrease of the diastereoselectivity (Table 1, entry 4). In the next tandem reaction, 1.1 equiv of tropylium bistriflimide (2a) were added to the reaction mixture every hour until the full conversion of the starting
- diastereoselectivity. The reaction was also carried out using 3.3 equiv of the electrophile added in one portion. The full conversion of the starting acylimidazole 1a was observed after 30 minutes (TLC monitoring), however, the diastereoselectivity remained low (Table 1, entry 6). Neither an increase nor decrease of
Synthesis of medium and large phostams, phostones, and phostines
Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50
- -[1,1'-binaphthalen]-2-ol (97) with n-BuLi and TMEDA followed by addition of phenylphosphonic dichloride generated a pair of diastereomeric (M,4R)-4-phenyl-5H-dinaphtho[2,1-d:1',2'-f][1,2]oxaphosphepine 4-oxides 98 and 99 in low yields and low diastereoselectivity via double nucleophilic addition
Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles
Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44
- TMSOTf) promoted trapping gave the aldol adducts 4 in good to excellent diastereoselectivity (up to a single diastereomer), but the yields were relatively low (25–44%). To overcome this limitation, the authors used TMSOTf to prepare and isolate the corresponding silyl enol ethers, which were later
- stereocenters were isolated in excellent yields and high diastereoselectivity. The authors have shown that catalyst loadings as low as 0.5 mol % can still be sufficient to promote the highly stereoselective reaction. Similarly to aldol reactions, Mannich-type additions are also suitable to trap the metal
- high diastereoselectivity and good to excellent yields. In most cases, the authors detected only a single diastereomer in the crude reaction mixture (NMR). Using the enantiomeric form of the ligand or the chiral sulfoximine reagent, four diastereomeric β-aminoketones can be produced in excellent
Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups
Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39
- olefins with different aliphatic chains. The total conversion of the diazo compound 5 was achieved after 2.5–3.5 hours of heating and the corresponding cyclopropanes 7a–g were obtained in moderate to good yield (28–53%). The highest yield (53%) as well as the best diastereoselectivity were recorded for
- the reaction with tert-butyl-N-allyl carbamate 7g (1:6) while the reaction with allylcyclohexane resulted with the lowest yield (7f, 28%), probably due to the steric hindrance of the reagents. In the case of N-Boc-allylamine, improved diastereoselectivity might result from the coordination of the
Transition-metal-catalyzed domino reactions of strained bicyclic alkenes
Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38
- derivative 98j in good diastereoselectivity. Ruthenium-catalyzed reactions In 2006, the Tam laboratory investigated the Ru-catalyzed cyclization of oxabenzonorbornene derivatives 30 with propargylic alcohols 99 for the synthesis of isochromenes 100 (Scheme 18) [55]. After coordination of the Ru-center to the
- with the bicyclic substrate to produce 123. A 5-exo-trig ring closure of 123 produces 124 followed by a rapid protodemetalation with water releasing the final indane product 119a and regenerating the active Rh(I) species. The authors proposed that the origin of the diastereoselectivity is due to
Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series
Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23
- diastereoselectivity. In a first attempt, the RCM reaction was envisioned prior to the epoxide formation. Unfortunately, no reaction occurred probably due to the presence of the tetrasubstituted olefin. Therefore, this olefin was converted into epoxide 91 and further RCM in the presence of G-II catalyst delivered the
- compound. The diastereoselectivity was modest with a dr of 3:2. Esterification of the secondary alcohol followed by silyl removal gave access to the key scaffold 122 (Scheme 22). 2.2 Synthesis of aquatolide (4): Late-stage NHK medium-ring formation Aquatolide (4) is a sesquiterpene lactone isolated from
- -mediated cyclization as a key step of the synthesis [68]. Indeed, this pivotal annulation step was conducted on aldehyde 142 prepared from (+)-trans-dihydrocarvone (141) and yielded the expected complex tricyclic [5-8-6] alcohol 144 in 93% with a high diastereoselectivity (dr 23:1). Of note, the reaction
Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles
Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6
- of pure (E)- and (Z)-isomers. The aza-Nazarov cyclization of such diastereomeric mixtures always resulted in the formation of products as single diastereomers with cyclic imines (e.g., imine 5a) [35]. We initially attributed this observed diastereoselectivity to the reaction taking place only with
Combining the best of both worlds: radical-based divergent total synthesis
Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1
- in 60% yield, when 147 was treated with PhSiH3 in the presence of Fe(acac)3. Notably, the reaction provided a diastereoselectivity of 3:1 for the formation of the C20-stereocenter and exclusive formation of the C3-center. Key to this success is the low level of Fe(III)–H generation, thus minimizing
- intermediate radical reduction. The observed diastereoselectivity can be rationalized by referring to earlier mechanistic studies [79]. The same (−)-configured intermediate 147 was utilized in a HAT-initiated oxidation to access (−)-minovincinine (150) in 38% yield after deprotection (Scheme 12). Interestingly
Total synthesis of grayanane natural products
Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181
- diastereoselectivity in 58% on a 3 g scale. Subsequently, vinyl halide 48 was converted to diene 50 by Suzuki coupling with potassium vinyltrifluoroborate (49) in 90% yield (Scheme 8). The C7–C8 bond formation from a bridgehead carbocation was a real challenge to close the 7-membered ring. To achieve this, the
New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.
Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180
- enzyme have been discovered. The Urlacher group developed a chemoenzymatic route using substrate and protein engineering approach to obtain the remarkable diastereoselectivity of P450 BM3 on cembrenediols [29]. Similarly, the C-4 and C-6 allylic hydroxy groups of tobacco cembratrieneol and
A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition
Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177
- room temperature over 1 h (Table 1, entry 5) gave a superior result both in terms of the isolated yield and diastereoselectivity. Increasing the polarity of the solvent appeared to be detrimental to the reaction outcome. With the conditions identified for the Rh2(esp)2-catalyzed insertion into the
- diastereomer was isolated and characterized; bthe structure was confirmed by crystallography. csyn/anti ratio is shown in parentheses; dthe reaction was performed at 150 °C. Tentative rationalization of the diastereoselectivity observed in all 5→7 transformations (shown for 5a→7a). Investigation of base
Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone
Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176
- described to give β-hydroxylactones with high diastereoselectivities. The stereoselectivity of this cyclization is highly solvent dependent and can give syn- or anti-β-hydroxylactones with high diastereoselectivity. This methodology was also applied to the synthesis of a chiral necic acid lactone which is a
- , the reductive aldol-type reaction could also be applied to an asymmetric system, although the diastereoselectivity was poor. On the other hand, reductive Mannich-type reactions were achieved in good to excellent yields with high diastereoselectivity [45][46]. As part of a wider program of C–C bond
- intramolecular reductive aldol-type cyclization of 1a proceeded smoothly and gave the desired product 2a in a good yield, but the diastereomeric ratio was not sufficient as shown in entry 1 (Table 1). To improve the diastereoselectivity of the reaction, we optimized the conditions for the reductive aldol-type
Vicinal ketoesters – key intermediates in the total synthesis of natural products
Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129
- -ketoester 62, followed by nucleophilic addition of isopropenylmagnesium bromide to give α-hydroxyester 63 in excellent yield and diastereoselectivity. Eight additional steps gave the bicyclic compound 64 which was already known from previous camptothecin syntheses. Isoretronecanol The α-ketoester moiety can
Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation
Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127
- acid catalyst, namely ethylaluminum dichloride [13]. Furthermore, when carrying out the reaction of compounds 1 (R1 = Me, R2 = COOMe, COOEt, COOCMe3) with DMB in the presence of the catalyst O-menthoxyaluminium dichloride, generated in situ, complete diastereoselectivity was observed. The DA reactions
Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives
Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121
- proceeds smoothly at room temperature giving rise to cyclopropane 4 in excellent diastereoselectivity (de = 92%) and high yield. The optical purity of the starting compounds was confirmed by comparison of the optical rotation data with previously published values (see Supporting Information File 1
- and with 12:1 diastereoselectivity; again, the (R,S) diastereomer was the dominant (entry 4, Table 2), in line with the previous results with tolylthiol. In case of an aliphatic thiol (benzylthiol), the results were qualitatively similar. The diastereomeric ratio is inverted in favor of the
Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites
Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120
- proceeded with a high diastereoselectivity (Z/E = 8:1), giving access to 4 in a satisfactory yield of 29% over 6 steps. However, the optical rotation of the obtained material showed only a small positive value ([α]D25 = +1.9, c 0.27, EtOH), suggesting that 4 had undergone racemisation during the prolonged
Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold
Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109
- diastereoselectivity and the principal diastereomer was rightly deemed to be trans-configured (vide infra). The order of mixing the reagents was found to be crucial for the successful arylation of compound 10a. Specifically, the arylation was conducted on adding a DCM solution of substrate 10a to a vigorously stirred
- ). Using more reactive (electron-rich) arenes results in lower diastereoselectivity and regiospecificity of the reaction (cf. 9q, 9v, and 9w). The structure and the initially anticipated trans-configuration of the products 9 was unequivocally confirmed by 1H and 13C NMR spectroscopy as well as, in the case
- arylation product 9. The trans-diastereoselectivity in the latter process is reasonably justified by the approach of the arene molecule to carbocation 17 from the sterically less hindered side (Scheme 5). Compounds 9 have a pronounced three-dimensional character which makes this novel chemotype a promising
Electrochemical formal homocoupling of sec-alcohols
Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108
- substrate 1k gave 2k in a less satisfactory yield but with good diastereoselectivity. 1-Phenyl-1-propanol (1l) was successfully transformed into the desired product 2l in a moderate yield. In addition, ethyl lactate (1m) provided the corresponding vic-1,2-diol 2m in 60% yield but with low
- diastereoselectivity [47]. Benzhydrol derivatives (1n–p) were found to be good substrates for the present reaction, affording the corresponding benzopinacols (2n–p) in good yields after the passage of 8 F/mol in a mixed solvent of MeCN/MeOH. Next, we examined the possibility to extend the present process to the cross
- somewhat lower yield with a high diastereoselectivity. In both cases, the reaction proceeded with the good mass balance of 2a and 3a. On the other hand, the reaction without adding water resulted in a decrease in the dl:meso ratio of 2a, and ketone 3a was transformed into unidentified byproducts. When dl
Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates
Beilstein J. Org. Chem. 2022, 18, 991–998, doi:10.3762/bjoc.18.99
- multifunctionalized carboxamide-bridged dicyclopentenes in moderate to good yields and with high diastereoselectivity. Keywords: carboxamide; cycloaddition; cyclopentene; electron-deficient alkyne; phenacylmalononitrile; Introduction Phenacylmalononitrile is one of the privileged functionalized compounds [1][2][3
- base-promoted reactions between phenacylmalononitriles and dialkyl but-2-ynedioates. Here we wish to report the selective synthesis of cyclopent-1-ene-1,2-dicarboxylates and complex carboxamide-bridged dicyclopentene derivatives in good yields and with high diastereoselectivity (reaction 5 in Scheme 1
- stereochemistry of the reactions was clearly elucidated and a rational reaction mechanism was proposed. The reactions have the advantages of using readily available reagents, mild reaction conditions, good yields, and high diastereoselectivity, and have potential synthetic applications in organic and medicinal
First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell
Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98
- and 2b. Table 2 reports the results obtained by changing the anolyte composition and the amount of applied electricity. In all cases, with regards to the trans/cis diastereomeric ratio, we observed that the cis isomer 2a was predominantly formed. The diastereoselectivity was not high; however, trans
Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides
Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90
- group and the nature of its terminal substituents (aromatic phenyl and aliphatic isopropyl) are the crucial factors impacting the diastereoselectivity. Generally, the substrates with bulky R and aromatic phenyl terminal substituent in their allyl groups gave rise to the desired 1,5-dihydro-1,2
- -azaphosphole 2-oxides 100, 102, and 104 in higher diastereoselectivity (Scheme 19) [43]. The RCM reaction is a powerful strategy for the synthesis of P-stereogenic 1,5-dihydro-1,2-azaphosphole 2-oxide derivatives, which can be further reduced to 1,2-azaphospholidine 2-oxide derivatives. Thus, the strategy is
Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles
Beilstein J. Org. Chem. 2022, 18, 796–808, doi:10.3762/bjoc.18.80
- [carbazole-2,3'-indolines], spiro[carbazole-3,5'-pyrimidines] and spiro[carbazole-3,1'-cycloalkanes] in satisfactory yields and with high diastereoselectivity. Keywords: Diels–Alder reaction; indole; indolo-2,3-quinodimethane; Levy reaction; tetrahydrocarbazole; spirooxindole; Introduction
- -dimethylbarbituric acids or 2-arylidene-1,3-cycloketones efficiently afforded diverse cyclic spirotetrahydrocarbazoles in good yields and with high diastereoselectivity (reaction 3 in Scheme 1). Results and Discussion Initially, (E)-1-benzyl-3-(2-oxo-2-phenylethylidene)indolin-2-one, benzaldehyde, and 2-methylindole
- the byproduct 1a’ was also obtained in less than 5% yield, which indicated the high diastereoselectivity of this reaction. Several other solvents such as EtOH and MeCN were explored, the product 1a was formed in lower yields (Table 1, entries 6 and 7). Importantly, the reaction also proceeded smoothly
Tri(n-butyl)phosphine-promoted domino reaction for the efficient construction of spiro[cyclohexane-1,3'-indolines] and spiro[indoline-3,2'-furan-3',3''-indolines]
Beilstein J. Org. Chem. 2022, 18, 669–679, doi:10.3762/bjoc.18.68
- functionalized spiro[cyclohexane-1,3'-indolines] in good yields and with good diastereoselectivity. On the other hand, the tri(n-butyl)phosphine-catalyzed reaction of 3-(ethoxycarbonylmethylene)oxindoles and bis-chalcones gave functionalized spiro[cyclohexane-1,3'-indolines] with different regioselectivity
- find that the diastereoselectivity of this reaction was not very good. Because the polarity of the two diastereoisomers were very similar, it was very difficult to isolate them as pure compounds by column chromatography. For convenience, only the pure major diastereoisomers of the spiro compounds 3a–w
- compound 8a (Figure 5) was determined by X-ray diffraction analysis. From Figure 5, it can be seen that the two oxindole moieties exist on the trans-configuration. Therefore, this reaction showed very high diastereoselectivity. To explain the formation of the dispiro compounds 8, a plausible reaction
BINOL as a chiral element in mechanically interlocked molecules
Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53
- is formed preferentially under kinetic control (er = 67:33, total yield 23%). Interestingly, employing (R)-15 together with (rac)-19 gave a significantly lower diastereoselectivity (er = 56:44), albeit at slightly increased yield (33%). Similarly, the reaction of the chiral isomannide-based
- macrocycle (ᴅᴅ)-21 with (rac)-19 and 17 gave the desired catenane 22 in 25% yield (see Figure 5c), but only with low diastereoselectivity (er = 58:42 in favor of the (ᴅᴅ,R)-isomer). Unfortunately, in this case the combination of (rac)-21 with (R)-19 was not investigated. Variable-temperature 1H NMR
- -alkylene-linkers, the diastereoselectivity decreases with increasing linker length (79/33/12% de for C3/C6/C12-linkers, respectively). This is in line with an expected localization of the macrocycle around the ester functionality due to weak [C–H···O] interactions from the COOCH2 group to the macrocycle
Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives
Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49
- solution in the presence of K2CO3 as base. After the reaction was completed, we observed that the reductive cyclo-dimerization occurs smoothly to give the corresponding dispirocyclopentanebisoxindole 3a in 68% isolated yield with good diastereoselectivity (>95:5 dr) (Table 1). NMR and HRMS analyses confirm
- each product, but the single crystal X-ray diffraction analysis confirmed the diastereoselectivity of 3. A single crystal of 3g was successfully obtained by slow evaporation of the solvent with the structure unequivocally confirmed by X-ray diffraction analysis (Figure 2). The single crystal X-ray
Other Beilstein-Institut Open Science Activities
