A Heniconuclear {Mn₂₁} Cluster-Based Coordination Polymer with Manganese(II) Linkers Showing High Proton Conductivity

An unprecedented metal-linked cluster-based coordination polymer, composed of heniconuclear {Mn21} clusters and Mn­(II) ions as the nodes and linkers, respectively, was self-assembled from a facile aqueous synthesis. The structural analysis reveals that the compound possesses a rare 3D 8-connected hex framework topology. Significantly, the compound demonstrates a high proton conductivity of 1.06 mS cm–1 at 373 K and 98% RH and exhibits a magnetocaloric effect with a magnetic entropy change of −9.94 J kg–1 K–1 at H = 80 kOe and T = 6.0 K

A Practical Preparation of Ethyl <i>N</i>-Acyl-2-(dimethoxyphosphoryl)glycinate

A practical, cost-effective preparation of ethyl N-acyl-2-(dimethoxyphosphoryl)glycinate has been developed. The two-step process achieved an 80% overall isolated yield

DataSheet1_A Band-Notched Antenna With Two Radiation Zeros Using Grounded Coplanar Waveguide Filter for 2.4/5 GHz WLAN Applications.docx

In this article, a band-notched dual-polarized crossed dipole antenna is proposed for 2.4/5 GHz WLAN applications. The proposed antenna works on the WLAN 2.4-GHz (2.4–2.48 GHz) and 5-GHz (5.15–5.85 GHz) bands for a VSWR <2 with two radiation zeros within 3.4–3.6 GHz. First, an ultra-wideband crossed dipole antenna with an operating frequency of 2.4–5.8 GHz is designed using the grounded coplanar waveguide (GCPW) feeding structure. Second, a miniaturized defected microstrip structure (DMS) is embedded in the GCPW feeding strip to form a stopband behavior with a radiation zero. Finally, combining with the design of a C-shaped split ring resonator (SRR) on the arms of the dipole antenna, a band notch (3.4–3.6 GHz) with two radiation zeros can be realized. These two radiation zeros can be adjusted independently to achieve a wide stopband performance. As a result, compared with the original ultra-wideband dipole antenna, the realized gains of the proposed antenna in the 3.4–3.6 GHz range are all suppressed from 8 dBi to less than −8 dBi. The proposed antenna can realize the stable unidirectional radiation pattern and a high gain of around 7 dBi in the lower band and 8.5 dBi in the higher band of WLAN. As a demonstration, the proposed antenna is fabricated and measured, and the measurement results are in good agreement with the simulation results.</p

Syntheses of Strychnan- and Aspidospermatan-Type Alkaloids. 10. An Enantioselective Synthesis of (−)-Strychnine through the Wieland−Gumlich Aldehyde

Condensations of l-tryptophan-derived 2-[(methoxycarbonyl)methyl]-3-[2(S)-(benzyloxycarbonyl)-2-(Nb-benzylamino)ethyl]indole (6) with 4,4-dimethoxyacrolein or with 2,4-hexadienal, followed by removal of the tryptophanyl ester function, respectively gave the tetracyclic acetal (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(dimethoxymethyl)-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (10) or the tetracyclic olefin (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(1-propenyl)-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (14). Their respective hydrolysis or oxidation provided, enantioselectively, the tetracyclic aldehyde (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-formyl-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (5). Its reaction with tri-n-butyl-1-(ethoxy)ethoxymethyltin and n-butyllithium, followed by oxidation of the resultant alcohol (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(1ξ-hydroxy-2-((1-ethoxyethoxy))ethyl-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (16) and cyclization furnished the pentacyclic ketone (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-3,5-ethano-12-oxo-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (15). A Horner−Emmons condensation led to the unsaturated esters (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-3,5-ethano-12-(E and Z)-[(methoxycarbonyl)-methylene]-1H-pyrrolo[2,3-d]carbazole-6-carboxylates (19 and 20) with 17:1 E/Z selectivity. Reductions of the ester and vinylogous urethane functions in 19 led to the Wieland−Gumlich aldehyde 3 as a 6:1 anomeric hemiacetal mixture. Its condensation with malonic acid provided (−)-strychnine (1) in 5.3% overall yield and 14 steps from the tryptophan derivative 6

Syntheses of Strychnan- and Aspidospermatan-Type Alkaloids. 10. An Enantioselective Synthesis of (−)-Strychnine through the Wieland−Gumlich Aldehyde

Condensations of l-tryptophan-derived 2-[(methoxycarbonyl)methyl]-3-[2(S)-(benzyloxycarbonyl)-2-(Nb-benzylamino)ethyl]indole (6) with 4,4-dimethoxyacrolein or with 2,4-hexadienal, followed by removal of the tryptophanyl ester function, respectively gave the tetracyclic acetal (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(dimethoxymethyl)-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (10) or the tetracyclic olefin (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(1-propenyl)-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (14). Their respective hydrolysis or oxidation provided, enantioselectively, the tetracyclic aldehyde (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-formyl-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (5). Its reaction with tri-n-butyl-1-(ethoxy)ethoxymethyltin and n-butyllithium, followed by oxidation of the resultant alcohol (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(1ξ-hydroxy-2-((1-ethoxyethoxy))ethyl-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (16) and cyclization furnished the pentacyclic ketone (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-3,5-ethano-12-oxo-1H-pyrrolo[2,3-d]carbazole-6-carboxylate (15). A Horner−Emmons condensation led to the unsaturated esters (−)-methyl (2S,3aS,5R,11bR)-3-benzyl-2,3,3a,4,5,7-hexahydro-3,5-ethano-12-(E and Z)-[(methoxycarbonyl)-methylene]-1H-pyrrolo[2,3-d]carbazole-6-carboxylates (19 and 20) with 17:1 E/Z selectivity. Reductions of the ester and vinylogous urethane functions in 19 led to the Wieland−Gumlich aldehyde 3 as a 6:1 anomeric hemiacetal mixture. Its condensation with malonic acid provided (−)-strychnine (1) in 5.3% overall yield and 14 steps from the tryptophan derivative 6

Syntheses of Strychnan- and Aspidospermatan-Type Alkaloids. 11. Total Syntheses of (−)-Lochneridine and (−)- and Racemic 20-<i>epi</i>-Lochneridine

Enantioselective syntheses of (−)-lochneridine (1) and (−)-epi-lochneridine (2) were obtained by two alternative C-20 diastereoselective syntheses of the respective pentacyclic (3aS,5S,11bR)-methyl 12-oxo-3,5-ethano-2,3,3a,4,5,7-hexahydro-3H-pyrrolo[2,3-d]carbazole-6-carboxylate ((−)-8) and tetracyclic methyl (2S,3aS,5R,11bR))-3-benzyl-2,3,3a,4,5,7-hexahydro-5-(2-(1-butenyl))-1H-pyrrolo[2,3-d]carbazole-6-carboxylate ((−)-12b) precursors from tryptophan derived 2-[(methoxycarbonyl)methyl]-3-[2(S)-(methoxy or benzyloxycarbonyl)-2-(Nb-benzyl)aminoethyl]indole (15 or 16). While a modified Grignard reaction of the ketone (−)-8 provided (−)-lochneridine (1), dihydroxylation and cyclization of the olefin (−)-12b gave its C-20 epimer (2)

Syntheses of Strychnan- and Aspidospermatan-Type Alkaloids. 9. The Enantioselective Generation of Tetracyclic ABCE Intermediates by a Tandem Condensation, [3,3]-Sigmatropic Rearrangement, and Cyclization Sequence

Reactions of substituted acroleins with the tryptophan-derived benzyl 2-(benzylamino)-3-[3-[2-[(methoxycarbonyl)methyl]indolyl]]propionate gave tetracyclic hexahydro-1H-pyrrolo[2,3-d] intermediates with stereoselective placement of substituents for cyclization to pentacyclic Strychnos alkaloids. The benzyl ester moiety was readily removed by formation of a corresponding nitrile and reduction, thus providing enantioselective syntheses of the tetracyclic compounds

One-Step RhCl₃-Catalyzed Deprotection of Acyclic <i>N</i>-Allyl Amides

A convenient one-step RhCl3-catalyzed deprotection of acyclic N-allyl amides is described. Preliminary mechanistic studies reveal that the key to the success of the one-step deprotection process is the dual function of RhCl3 in alcohol solvents. Reaction of RhCl3 with n-PrOH not only provides an active rhodium hydride species to catalyze isomerization of N-allyl amides to corresponding enamides but also generates a crucial catalytic amount of HCl to convert the enamides to deallylated amides through N,O-acetal exchange

Simulation codes for PDE and generalised Landau– Levich equation

Simulation codes for PDE and generalised Landau– Levich equatio

One-Step RhCl₃-Catalyzed Deprotection of Acyclic <i>N</i>-Allyl Amides

A convenient one-step RhCl3-catalyzed deprotection of acyclic N-allyl amides is described. Preliminary mechanistic studies reveal that the key to the success of the one-step deprotection process is the dual function of RhCl3 in alcohol solvents. Reaction of RhCl3 with n-PrOH not only provides an active rhodium hydride species to catalyze isomerization of N-allyl amides to corresponding enamides but also generates a crucial catalytic amount of HCl to convert the enamides to deallylated amides through N,O-acetal exchange