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Search for "switch" in Full Text gives 182 result(s) in Beilstein Journal of Organic Chemistry.
A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions
- Falk Wehmeier and
- Jochen Mattay
Beilstein J. Org. Chem. 2010, 6, No. 53, doi:10.3762/bjoc.6.53
- diarylethene unit (3) can be obtained by lithiation of 3-bromo-2-methylbenzo[b]thiophene (1) followed by quenching with perfluorocyclopentene (2), according to the method described by Irie [12]. Electrophilic iodination leads to the diiodo photoswitch 4 (Scheme 1) [13][14]. We decided to use the diiodo switch
- 4 for catalytic cross coupling reactions, since approaches to a direct terpyridine synthesis, starting from suitable diarylethene aldehydes (Kröhnke condensation), were unsuccessful. Moreover, the diiodo switch 4 has been previously used for Suzuki-type cross coupling reactions [14]. Synthetic
- acid derivatives 9a [16] and 9b (Scheme 2). The terpyridine moieties can be attached to the diarylethene unit by Suzuki type cross coupling of the diiodo switch 4 with the boronic esters 9a and 9b under conditions similar to those described for other aryl boronic acids and their derivatives to yield
Graphical Abstract
Scheme 1: Synthesis of twofold iodinated bis(benzo[b]thiophenyl)perfluorocyclopentene 4.
Scheme 2: Synthesis of terpyridinyl boronic acids 9a and 9b.
Scheme 3: Synthesis of the bis(terpyridinyl)diarylethenes 10a and 10b.
Scheme 4: Photochromic reaction of the free ligand 10a.
Figure 1: UV–vis-spectra of 10a before (solid), after UV-irradiation (dashed) and after irradiation with vis ...
Scheme 5: Synthesis of the binuclear Ru(II)-complex 12.
Figure 2: UV–vis-spectra of 12 before (solid), after UV-irradiation (dashed) and after irradiation with vis l...
Figure 3: UV–vis-spectra of 12 before (dashed), after UV-irradiation (dotted), the difference (solid) and fre...
Figure 4: UV–vis-spectra of [Fe2+@10a] before (solid), after UV-irradiation (dashed) and after irradiation wi...
Figure 5: UV–vis-spectra of [Zn2+@10a] before (solid), after UV-irradiation (dashed) and after irradiation wi...
Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF2
- Lukas J. Gooßen,
- Bettina Zimmermann and
- Thomas Knauber
Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43
- arene product was improved by adding molecular sieves to the reaction medium (entry 14). We were now able to switch from a DMF/DMSO mixture to the less toxic solvent N-methyl-2-pyrrolidone (NMP) without a decrease in yields (entry 15). Next, we investigated the influence of ligands on the performance of
Graphical Abstract
Scheme 1: Proposed mechanism for the decarboxylative Heck reaction.
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
Size selective recognition of small esters by a negative allosteric hemicarcerand
- Holger Staats and
- Arne Lützen
Beilstein J. Org. Chem. 2010, 6, No. 10, doi:10.3762/bjoc.6.10
- single receptor. This causes conformational rearrangements that switch on or off a function that is inherently embedded in the different parts of the molecule but which need to be specially arranged in space in order to act in an optimized cooperative fashion. Some time ago we were able to report on a
- 2,2′-bipyridine. This structure has proved to be an excellent allosteric centre [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] due to its well defined ability to switch between syn- and an anti-conformations [27]. Recently, we were able to synthesize a number of
- ). Thus, pentacarbonylrhenium(I) chloride seemed indeed an excellent effector here because it can be used to switch off 2 by coordination to the bipyridine and switch it on again when it is removed. When we repeated the titration with this complex we did observe some shifts of the host signals but these
Graphical Abstract
Scheme 1: Bis(resorcinarene) esters of 4,4′- and 4,6′-(2,2′-bipyridyl)dicarboxylic acid, 1 and 2, respectivel...
Scheme 2: Simple esters used as model substrates in this study.
Figure 1: Qualitative binding studies of 2 and the model substrates 3–7. 1H NMR spectra (500.1 MHz, 298 K in ...
Figure 2: 1H NMR titration (500.1 MHz, 298 K, c0(2) = 5.3 mmol/L) of 2 with increasing amounts of ethyl aceta...
Scheme 3: Binding model of the negative cooperative allosteric behaviour of 2.
Flow through reactors for organic chemistry: directly electrically heated tubular mini reactors as an enabling technology for organic synthesis
- Ulrich Kunz and
- Thomas Turek
Beilstein J. Org. Chem. 2009, 5, No. 70, doi:10.3762/bjoc.5.70
- through the tube was 56.66 A, while a voltage at the tube of 4.45 V was determined. This gives a power uptake of the tube of 252 W. All this power is transferred into heat. The voltage drop of 0.55 V is mainly caused by the voltage drop of the power MOSFET switch which is used to actuate the heating
- current. The voltage drop of the copper cables can be neglected. The loss of the power switch is 31 W which is approximately 10% of the power taken from the power supply, thus the power supply has an efficiency of 90%. This leads to a power consumption from the 230 V ~ AC line of about 314 W to deliver
- the power of 283 W for the heated tube and the 31 W for the power switch. The power consumption of the temperature controller is about 1 W and can be neglected. Thus the overall efficiency is roughly 80%. To give an impression for a reachable temperature increase: with a power of 252 W the temperature
Graphical Abstract
Figure 1: Experimental setup for heating tubular flow reactors by passing electric current directly through t...
Scheme 1: Acid catalyzed hydrolysis of methyl formate.
Figure 2: Conversion as a function of temperature for 3 different residence times.
Figure 3: Arrhenius plot for the measured rate constants.
Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)
- Henning Hopf,
- Christian Beck,
- Jean-Pierre Desvergne,
- Henri Bouas-Laurent,
- Peter G. Jones and
- Ludger Ernst
Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20
- . Because of its slow response and the fatigue observed in the photodissociation, this system does not seem suitable as a switch, but might be considered for applications such as optical storage [28], owing to the large spectral shift (Δmax ca 7500 cm−1) of the electronic absorption spectra between 2 (λmax
Graphical Abstract
Figure 1: Schematic representation of a photochromic system. The reverse reaction can be a photochemical or t...
Figure 2: Photochromic reaction of pseudo-gem disubstituted tetraene [2.2]cyclophane 1 in acetonitrile, conc....
Figure 3: Molecular structure of 4,13-bis[(1E,3E)-4-(9-anthracenyl)-buta-1,3-dienyl][2.2]paracyclophane (2).
Scheme 1: Preparation of 2 (last step), using the Wittig reaction. The preparation of 3 has been described in...
Figure 4: Molecular structure of 2 in the crystal. Radii are arbitrary; only selected H atoms are shown.
Figure 5: Projection of the molecular structure of 2 exhibiting the closest internuclear distances (distances...
Figure 6: Electronic absorption spectra of 2 (conc. ca 10−4 M) in MCH (full line) and CH3CN (dotted line) at ...
Figure 7: Irradiation of 2 (2.6 × 10−5 M) in CH3CN at 400 nm at 20 °C. The spectra were recorded at various t...
Figure 8: Irradiation at 306 nm of the photoproduct 4 obtained at 400 nm in the same setup; the spectra were ...
Figure 9: Reversibility of the formation of the photoproduct 4 at 400 nm (40 min) and photodissociation of 4 ...
Figure 10: 1H NMR spectra (400 MHz, CDCl3). A: Compound 2, B: Compound 4.
Figure 11: Proposed structure of 4 (1,4 : 2′,3′-cycloadduct).
Methods for the synthesis of polyhydroxylated piperidines by diastereoselective dihydroxylation: Exploitation in the two-directional synthesis of aza-C-linked disaccharide derivatives
- Andrew Kennedy,
- Adam Nelson and
- Alexis Perry
Beilstein J. Org. Chem. 2005, 1, No. 2, doi:10.1186/1860-5397-1-2
- elaboration of symmetrical substrates;[33] in this paper, we apply a two directional approach to the synthesis of highly unsymmetrical compounds. Indeed, a powerful feature of our approach is the potential to switch between two- and one-directional synthetic steps; for example selective substitution of the
- .) For the syntheses of the allylated and reduced substrates, the crude products were treated directly with boron trifluoride etherate and either allyltrimethylsilane or triethylsilane. It was possible to switch cleanly to a one-directional synthesis because the N,O acetals were much more susceptible to
- were hydrolysed to give the bis-allylic alcohols trans-34 and cis-34 respectively (Scheme 7). A key feature of our approach is the ability to switch as required between one- and two-directional synthetic modes as appropriate. We therefore investigated the possibility of selective inversion of one of
Graphical Abstract
Scheme 1:
Scheme 2:
Scheme 3:
Figure 1: Diastereoselective substitution of the N,O acetal 12
Scheme 4:
Figure 2: Diastereoselective Luche reduction of piperidinones
Scheme 5:
Figure 3: Diastereoselective dihydroxylation of unsaturated piperidines
Figure 4: Diagnostic nOe observations for the piperidine 22A
Figure 5: Diagnostic nOe observations for the piperidines 22C and 22D
Scheme 6:
Figure 6: Stereoselectivity of two-directional Luche reductions
Scheme 7:
Scheme 8:
Figure 7: Two-directional functionalisation by diastereoselective dihydroxylation
