Origin of the diastereoselection in the indium-mediated addition of haloallylic sulfones to aldehydes

[reaction: see text] The R(1) substituents at C(2) of the haloallylic sulfones 1 play a pivotal role in controlling the diastereoselectivity of the indium-mediated addition reaction to benzaldehyde to produce the homoallylic alcohols 3. The R(1) Me group of 1 prefers the chair form in the In-coordinated six-membered cyclic transition state to give anti-3a, and the R(1) Ph group of 1 favors the twist boat form to give syn-3n, both in a high 13:1 selectivity.     

Steric control of a bridging ligand for high-nuclearity metallamacrocycle formation: a highly puckered 60-membered icosanuclear metalladiazamacrocycle

A novel S4-symmetric icosanuclear manganese metalladiazamacrocycle was synthesized using a pentadentate ligand, N-3-phenyl-trans-2-propenoylsalicylhydrazide (H3L), that has a rigid and bulky terminal N-acyl group. A 20 cyclic repeat of an--(Mn-N-N)--linkage resulted in a highly puckered diaza-bridged 60-membered icosanuclear metallamacrocycle. The steric interaction between the ligands in the cyclic system leads to five consecutive Mn(III) centers in a chemically different--(Mn(A)Mn(B)Mn(C)Mn(D)Mn(E))--environment, with the chiralities of the metal centers being in a rather complicated--(LambdaLambdaDeltaLambdaLambda)(DeltaDeltaLambdaDeltaDelta)--sequence.     

Rearrangements of 5-acetyl-3-benzoylamino-6-(2-dimethylamino-1-ethenyl)-2H-pyran-2-one and 3-benzoylamino-6-(2-dimethylamino-1-ethenyl)-5-ethoxycarbonyl-2H-pyran-2-one into 1-aminopyridine,pyrano[2,3-b]pyridine and isoxazole derivatives

Rearrangements of 5-acetyl-3-benzoylamino-6-(2-dimethylamino-1-ethenyl)-2H-pyran-2-one ( 1 ) and 3-benzoylamino-6-(2-dimethylamino-1-ethenyl)-5-ethoxycarbonyl-2H-pyran-2-one ( 7 ) in the presence of N-nucleophiles, such as ammonia, hydrazine, and hydroxylamine, into 1-aminopyridine, pyrano[2,3-b]-pyridine, and isoxazole derivatives 5, 11 , and 15 is described. In the reaction of compounds 1 and 7 with C-nucleophiles, such as 5,5-dimethyl-1,3-cyclohexanedione and barbituric acid, only substitution of the dimethylamino group is taking place to give the compounds 17, 18 , and 20 .     

Size and shape selectivity of host networks built based on tunable secondary building units

By modulating the secondary building units derived from the primary building units, N-acylsalicylhydrazides (H3 xshz), we have been able to construct isostructural but tunable host networks, [Mn6(xshz)6(dmf)2(bpea)2], with different cavity sizes and shapes where the secondary building units, [Mn6(xshz)6], were linked through exo-bidentate bridging ligand, 1,2-bis(pyridyl)ethane (bpea) to form 3-D networks. With a short length linear N-acyl side chain at the primary building unit, the host networks have a 3-D network with three-dimensional cavities. With an appropriate length linear N-acyl side chain at the primary building unit, the host network keeps the isostructural 3-D network but with two types of one-dimensional channels of reduced cavity volume. The tuned host networks showed not only size selectivity for the guest molecules but also shape selectivity. While the three-dimensional channeled host showed selectivity depending on the length of the podal guests, the one-dimensional channeled host showed selectivity depending on both the length and/or the podality of the guest molecules.     

Synthesis and characterization of novel grid coordination polymer networks generated from unsymmetrically bridging ligands

Self-assembly between simple unsymmetrical ligands, such as 1-(3-pyridyl)-2-(4-pyridyl)ethene (L(1)) and 1-methyl-1'-(3-pyridyl)-2-(4-pyrimidyl)ethene (L(2)), and Co(NCS)(2) affords the unprecedented two-dimensional grid coordination polymers [Co(L(1))(2)(NCS)(2)](infinity) (1) and [Co(L(2))(2)(NCS)(2)](infinity) (2), respectively, with novel topological features which cannot be achieved using symmetrically bridging ligands.     

Stereoselective 1,3-Dipolar Cycloadditions to (S)-1-Benzoyl-3-(cyanomethylidene)-5-(methoxycarbonyl)pyrrolidin-2-one

(5S)-1-Benzoyl-3-[(E)-cyanomethylidene]-5-(methoxycarbonyl)pyrrolidin-2-one ( 5 ) was prepared in four steps from L -pyroglutamic acid ( 1 ). 1,3-Dipolar cycloadditions of diazomethane ( 6 ) and 2,4,6-trimethoxybenzonitrile oxide ( 7 ) gave substituted 1,2,7-triazaspiro[4.4]non-1-en-6-one 12 and 1-oxa-2,7-diazaspiro[4,4]non-1-en-6-one 13 in 38 and 20% de, respectively. On the other hand, reaction of 5 with N-phenylbenzonitrile imines 8 and 9 , generated in situ from the corresponding hydrazonoyl chlorides 10 and 11 , respectively, and Et₃N, furnished racemic pyrrolo[3,4-c]pyrazoles 14 and 15 in 61 and 56% de, respectively. Cycloaddition of nitrile oxide 7 , when performed in the presence of Et₃N, led to pyrrolo[3,4-d]isoxazole 16 in 85% de.     

Energetics in correlation with structural features: the case of micellization

Understanding micellization processes at the molecular level has direct relevance for biological self-assembly, folding, and association processes. As such, it requires complete characterization of the micellization thermodynamics, including its correlation with the corresponding structural features. In this context, micellization of a series of model non-ionic surfactants (poly(ethylene glycol) monooctyl ethers, C(8)E(gamma)) was studied by isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC). The corresponding structural properties of C(8)E(gamma) micelles were investigated by small-angle X-ray scattering (SAXS). The C(8)E(gamma) micellization, characterized independently from ITC, DSC, and structural data, reveals that deltaH(M)(o) > 0, deltaS(M)(o) > 0, and deltaC(P)(M)(o) < 0, while the dissection of its energetics shows that it is primarily governed by the transfer of 20-30 C(8) alkyl chains from aqueous solution into the nonpolar core (r approximately 1.3 nm) of the spherical micelle. Moreover, thermodynamic parameters of micellization, estimated from the structural features related to the changes in solvent-accessible surface areas upon micellization, are in a good agreement with the corresponding parameters obtained from the analysis of ITC and DSC data. We have shown that the contributions to deltaS(M)(o) other than from hydration (deltaS(M)(other)(o)), estimated from experimental data, appear to be small (deltaS(M)(other)(o) < 0.1 deltaS(M)(other)(o)) and agree well with the theoretical estimates expressed as a sum of the corresponding translational, conformational, and size contributions. These deltaS(M)(other)(o) contributions are much less unfavorable than those estimated for a rigid-body association, which indicates the dynamic nature of the C(8)E(gamma) micellar aggregates. the dynamic nature of the C8EY micellar aggregates.     

2‐Amino­thia­zole and 2‐amino­thiazolinone derivatives

The reaction of different substituted α‐cyano­oxiranes with thio­urea resulted in the formation of the 2‐amino­thia­zolinone derivative 2‐amino‐5‐(2,5‐di­methoxy­phenyl)‐1,3‐thia­zol‐4(5H)‐one, C₁₁H₁₂N₂O₃S, (I), and the 2‐amino­thia­zole derivative ethyl 2‐amino‐5‐(2,5‐di­methoxy­phenyl)‐1,3‐thia­zole‐4‐carboxyl­ate, C₁₄H₁₆N₂O₄S, (II). The geometries of the two crystallographically independent mol­ecules in (II) are nearly identical but mirror related. The crystal structures of both compounds contain two types of intermolecular hydrogen bonds.     

Robust and efficient amide-based nonheme manganese(III) hydrocarbon oxidation catalysts: substrate and solvent effects on involvement and partition of multiple active oxidants

Two new mononuclear nonheme manganese(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Mn(bpc)Cl(H₂O)] ( 1 ) and [Mn(Me₂bpb)Cl(H₂O)] ? CH₃OH ( 2 ), were prepared and characterized. Complex 2 has also been characterized by X‐ray crystallography. Magnetic measurements revealed that the complexes are high spin (S=5/2) Mn^III species with typical magnetic moments of 4.76 and 4.95 μ_B, respectively. These nonheme Mn^III complexes efficiently catalyzed olefin epoxidation and alcohol oxidation upon treatment with MCPBA under mild experimental conditions. Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants Mn^V?O, Mn^IV?O, and Mn^III? OO(O)CR. Evidence for this approach was derived from reactivity and Hammett studies, KIE (k_H/k_D) values, H₂¹⁸O‐exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. In addition, it has been proposed that the participation of Mn^V?O, Mn^IV?O, and Mn^III? OOR could be controlled by changing the substrate concentration, and that partitioning between heterolysis and homolysis of the O? O bond of a Mn‐acylperoxo intermediate (Mn? OOC(O)R) might be significantly affected by the nature of solvent, and that the O? O bond of the Mn? OOC(O)R might proceed predominantly by heterolytic cleavage in protic solvent. Therefore, a discrete Mn^V?O intermediate appeared to be the dominant reactive species in protic solvents. Furthermore, we have observed close similarities between these nonheme Mn^III complex systems and Mn(saloph) catalysts previously reported, suggesting that this simultaneous operation of the three active oxidants might prevail in all the manganese‐catalyzed olefin epoxidations, including Mn(salen), Mn(nonheme), and even Mn(porphyrin) complexes. This mechanism provides the greatest congruity with related oxidation reactions by using certain Mn complexes as catalysts.