由邻苯二胺合成苯并咪唑、喹喔啉以及1-H-2,3－二氢1,5-苯并氮杂卓

A series of benzo-fused heteroaromatic compounds with 5-, 6- and 7-membered tings, such as benzimidazole,quinoxaline and 1H-1,5-benzodiazepine derivatives, were synthesized through condensation reaction of o-pheny1-enediamine with ary1 aldehydes or ketones. The experimental conditions were carefully examined, and the products were characterized by ^1H NMR, ^13C NMR, MS, IR and elemental analyses. In addition, the structure of a benzodiazaepine derivative with 7-membered ring was confirmed by single crystal X-ray diffraction analysis.     

Novel Transition‐Metal (M=Cr,Mo, W,Fe) Carbonyl Complexes with Bis(guanidinato)silicon(II) Ligands

The donor‐stabilized silylene 2 (the first bis(guanidinato)silicon(II ) complex) reacts with the transition‐metal carbonyl complexes [M(CO)₆] (M=Cr, Mo, W) to form the respective silylene complexes 7 – 10 . In the reactions with [M(CO)₆] (M=Cr, Mo, W), the bis(guanidinato)silicon(II ) complex 2 behaves totally different compared with the analogous bis(amidinato)silicon(II ) complex 1 , which reacts with [M(CO)₆] as a nucleophile to replace only one of the six carbonyl groups. In contrast, the reaction of 2 leads to the novel spirocyclic compounds 7 – 9 that contain a four‐membered SiN₂C ring and a five‐membered MSiN₂C ring with a M?Si and M?N bond (nucleophilic substitution of two carbonyl groups). Compounds 7 – 10 were characterized by elemental analyses (C, H, N), crystal structure analyses, and NMR spectroscopic studies in the solid state and in solution.     

Total Synthesis of Talatisamine

Talatisamine ( 1 ) is a member of the C₁₉‐diterpenoid alkaloid family, and exhibits K⁺ channel inhibitory and antiarrhythmic activities. The formidable synthetic challenge that 1 presents is due to its highly oxidized and intricately fused hexacyclic 6/7/5/6/6/5‐membered‐ring structure (ABCDEF‐ring) with 12 contiguous stereocenters. Here we report an efficient synthetic route to 1 by the assembly of two structurally simple fragments, chiral 6/6‐membered AE‐ring 7 and aromatic 6‐membered D‐ring 6 . AE‐ring 7 was constructed from 2‐cyclohexenone ( 8 ) through fusing an N‐ethylpiperidine ring by a double Mannich reaction. After coupling 6 with 7 , an oxidative dearomatization/Diels–Alder reaction sequence generated fused pentacycle 4 b . The newly formed 6/6‐membered ring system was then stereospecifically reorganized into the 7/5‐membered BC‐ring of 3 via a Wagner–Meerwein rearrangement. Finally, Hg(OAc)₂ induced an oxidative aza‐Prins cyclization of 2 , thereby forging the remaining 5‐membered F‐ring. The total synthesis of 1 was thus accomplished by optimizing and orchestrating 33 transformations from 8 .     

Total Synthesis of Crotophorbolone

The complex ABC‐tricyclic structure of crotophorbolone, a derivative of the tigliane diterpenoids, was assembled by coupling of simple fragments. The six‐membered C‐ring fragment, having five contiguous stereocenters, was stereoselectively constructed from (R)‐carvone. After attachment of the five‐membered A‐ring through the π‐allyl Stille coupling reaction, the α‐alkoxy bridgehead radical reaction effected the endo‐cyclization of the seven‐membered B‐ring by forming the sterically congested bond at C9 and C10 stereospecifically and stereoselectively, respectively. Finally, the functional groups on the 5/7/6‐membered ring system were manipulated by rhodium‐catalyzed C2 olefin isomerization, C13 decarboxylative oxidation, and C4 hydroxylation, thus completing the first total synthesis of crotophorbolone.     

Mechanisms of norbornadiene dimerization to Binor‐S using cationic CoI,RhI, and IrI catalysts

We investigated the transition metal‐catalyzed reaction mechanisms of NBD dimerization to Binor‐S using cationic Co^I, Rh^I, and Ir^I catalysts, using mPW1PW91, mPW1K, and B3LYP density functional methods. Our results indicate that the monomeric metal center has the ability to bind with four double bonds of two NBD molecules with a syn spatial geometry to form a penta‐coordinated complex. We designed three possible pathways, but found two of them blocked. The favored pathway involves three steps from the reactant precursor to the product precursor: the first step is the formation of a single bond to connect two NBD units, the second is the alkene insertion leading to the formation of the three‐membered ring structure, and the final step is the formation of the final product precursor. Orbital analysis showed metal…C? C σ agostic interaction in the product precursor, which is in agreement with the previous experimental findings. In addition, we found that the solvent and counter‐ions had significant effects on the dimerization reactions. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Organometallic Diaza‐dimetalla‐Norbornanes and ‐Cyclohexanes of Aluminium,Gallium and Indium

Selective formation of 1,3,3,4,6,6‐hexamethyl‐1,4‐diaza‐3,6‐diinda‐norborane was achieved by the reaction of bis(lithiomethyl‐methylamino)methane with dimethylindium chloride by simultaneous formation of two dative metal‐carbon and two metal‐nitrogen bonds accompanied by two ring closures. The synthesis of heterometallic compounds of this type, namely 1,3,3,4,6,6‐hexamethyl‐3‐alumina‐1,4‐diaza‐6‐galla‐norborane [Me₂AlCH₂N(Me)]CH₂[N(Me)CH₂GaMe₂], was also attempted by the reaction of bis(lithiomethyl‐methylamino)methane with dimethylaluminium and ‐gallium chloride. This compound is formed, but cannot be separated from the simultaneously formed homometallic compounds [Me₂MCH₂N(Me)]₂CH₂(M = Al, Ga). The compounds were identified by elemental analyses, mass spectra, NMR spectroscopy (¹H, ¹³C), and by determination of their crystal structures in which they are present as monomers. The norbornane‐like structure is favoured over potential isomers containing three‐membered rings and over polymeric aggregation in both compounds. In addition, the crystal structure of dimethyl(dimethylaminomethyl)indium was determined by single crystal X‐ray diffraction, which shows an intermolecular aggregation into a six‐membered ring dimer.     

Total Synthesis of 1‐Hydroxytaxinine

1‐Hydroxytaxinine ( 1 ) is a cytotoxic taxane diterpenoid. Its central eight‐membered B‐ring possesses four oxygen‐functionalized centers (C1, C2, C9, and C10) and two quaternary carbon centers (C8 and C15), and is fused with six‐membered A‐ and C‐rings. The densely functionalized and intricately fused structure of 1 makes it a highly challenging synthetic target. Reported here is an efficient radical‐based strategy for assembling 1 from A‐ and C‐ring fragments. The A‐ring bearing an α‐alkoxyacyl telluride moiety underwent intermolecular coupling with the C‐ring fragment by a Et₃B/O₂‐promoted decarbonylative radical formation. After construction of the C8‐quaternary stereocenter, a pinacol coupling reaction using a low‐valent titanium reagent formed the B‐ring with stereoselective installation of the C1,C2‐diol. Subsequent manipulations at the A‐ and C‐rings furnished 1 in 26 total steps.     

Adduct Formation,B−H Activation and Ring Expansion at Room Temperature from Reactions of HBcat with NHCs

We report the reactions of catecholborane (HBcat; 1 ) with unsaturated and saturated NHCs as well as CAAC^Me. Mono‐NHC adducts of the type HBcat?NHC (NHC=nPr₂Im, iPr₂Im, iPr₂Im^Me, and Dipp₂Im) were obtained by stoichiometric reactions of HBcat with the unsaturated NHCs. The reaction of CAAC^Me with HBcat yielded the B?H activated product CAAC^Me(H)Bcat via insertion of the carbine‐carbon atom into the B?H bond. The saturated NHC Dipp₂SIm reacted in a 2:2 ratio yielding an NHC ring‐expanded product at room temperature forming a six‐membered ?B?C=N?C=C?N? ring via C?N bond cleavage and further migration of the hydrides from two HBcat molecules to the former carbene‐carbon atom.     

(1R,3S)‐Camphoramic acid

The title chiral compound, 3‐amino­carbonyl‐1,2,2‐tri­methyl­cyclo­pentane‐1‐carboxylic acid, C₁₀H₁₇NO₃, was prepared from (1R,3S)‐camphoric acid. The five‐membered ring adopts a conformation which is intermediate between a twist and an envelope. Elongations of the C—C bonds and contractions of the C—C—C bond angles are observed within the five‐membered ring. A ¹H NMR spectrum was recorded to assist in distinguishing the amide group from the carboxyl group.     

蒂巴茵衍生物的合成研究

The reaction of 7α-acetyl-6,14-endoethano-6,7,8,14-tetrahydrothebaine with 2-（thien-2-yl）ethylmagnesium bromide was investigated. The tertiary alcohol derivative 7α-[R-l-hydroxyl-l-methyl-3-（thien-2-yl）propyl]）-6,14- endoethano-6,7,8,14-tetrahydrothebaine （3） and a by-product 4 were isolated. The structure of 4 was elucidated by X-ray analysis. The Grignard reaction shows high degree of stereoselectivity according with Cram rule. The crystal structure of 4 indicates that dihydrofuran ring was opened to form a phenolic hydroxyl group and a three-membered ring structure. It maintains the main rigid structure of morphine and contains a C（6）-C（14） enthano bridge. The 1-hydroxyl-1-methyl-3-（thien-2-yl）propyl group at C（7） position adopted S-configuration.     

Kinetic and Mechanistic Insights into the Pathway Leading to Cyclic Crystalline Phosphorus Ylide Formation in the Presence of 3‐Chloropentane‐2,4‐dione: Theoretical and Stopped‐Flow Approaches

In this work, three speculative mechanisms of the reaction between triphenylphosphine and dimethyl acetylendicarboxylate in the presence of 3‐chloropentane‐2,4‐dione were energetically and thermodynamically developed using quantum mechanical calculations and were profoundly compared with stopped‐flow and UV spectrophotometry approaches. The third speculative mechanism that led to the five‐membered ring structure was experimentally and theoretically favorable. The five‐membered ring structure of product was characterized by X‐ray crystallographic data. Also, steps 1 and 2 of the third mechanism were determined as fast and rate‐determining steps, respectively. The experimental kinetic evidence of the formation and decay of intermediate in steps 1 and 2 (fast and rate‐determining steps, respectively) was compatible with theoretical data. Experimental kinetic data were recognized for overall reaction along with activation parameters for fast and rate‐determining steps of the reaction. Theoretical kinetic data (k and E_a) and activation parameters (ΔG^≠, ΔS,^≠ and ΔH^≠) were calculated for each step and overall reactions.     

Cyclopolymerization of perfluoroisopropenyl vinylacetate

To develop the polymerization exploiting the interconversion of fluorinated carbon radical to hydrocarbon radical, the radical cyclopolymerization of perfluoroisopropenyl vinylacetate [CF₂?C(CF₃)OCOCH₂CH?CH₂] (FIA) was investigated to afford a polymer possessing mainly five‐membered ring structure with bimodal molecular weight distribution having 1 × 10⁵ as the higher molecular weight. This may be the first example wherein the cyclopolymerization between usual allyl group and fluorinated vinyl group is performed. The degree of cyclization was between 70 and 80% determined by ¹⁹F NMR of as‐polymerized products. The polymer preparation from perfluoroisopropenyl group, which shows scarce homopolymerization reactivity was accomplished. The mechanism that the addition of hydrocarbon radical to perfluoroisopropenyl group to produce fluorinated carbon radical followed by the intramolecular addition reaction onto allyl group to form five‐membered ring is proposed. The hydrolysis of the FIA polymer afforded a polymer possessing hydrophobic fluoroalkyl group with hydrophilic hydroxyl and carboxylic acid groups. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3220–3232, 2006     

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil,a cyclouridine nucleoside with a C4′‐endo furanosyl conformation

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil, C₁₃H₁₄N₂O₇, was obtained by refluxing 2′,3′‐O‐(methoxymethylene)uridine in acetic anhydride. The structure exhibits a nearly perfect C4′‐endo (⁴E) conformation. The best four‐atom plane of the five‐membered furanose ring is O—C—C—C, involving the C atoms of the fused five‐membered oxazolidine ring, and the torsion angle is only −0.4 (2)°. The oxazolidine ring is essentially coplanar with the six‐membered uracil ring [r.m.s. deviation = 0.012 (5) Å and dihedral angle = −3.2 (3)°]. The conformation at the exocyclic C—C bond is gauche–trans which is stabilized by various C—H...π and C—O...π interactions.     

Palladium‐Catalyzed Desymmetrization of Silacyclobutanes with Alkynes to Silicon‐Stereogenic Silanes: A Density Functional Theory Study

The palladium‐catalyzed desymmetrization of silacyclobutanes using electron‐deficient alkynes proceeds with high enantioselectivity in the presence of a chiral P ligand; this provides a facile approach for the synthesis of novel silicon‐stereogenic silanes. In this work, we used hybrid density functional theory (DFT) to elucidate the mechanism of the palladium‐catalyzed desymmetrization of silacyclobutanes with dimethyl acetylenedicarboxylate. Full catalytic cycle including two different initiation modes that were proposed to be a possible initial step to the formation of the 1‐pallada‐2‐silacyclopentane/alkyne intermediate—the oxidative addition of the palladium complex to the silacyclobutane Si?C bond (cycle MA) or coordination of the Pd⁰ complex with the alkyne C≡C bond (cycle MB)—have been studied. It was found that the ring‐expansion reaction began with cycle MB is energetically more favorable. The formation of a seven‐membered metallocyclic Pd^II intermediate was found to be the rate‐determining step, whereas the enantioselectivity‐determining step, oxidative addition of silacyclobutane to the three‐membered metallocyclic Pd^II intermediate, was found to be quite sensitive to the steric repulsion between the chiral ligand and silacyclobutane.     

Synthesis and Characterization of a Novel Two‐Dimensional Network Polymer Containing 18‐ and 26‐Membered Organotin Macrocycles

The reaction of 4‐mercaptophenylacetic acid with dimethyltin dichloride in the presence of sodium ethoxide in ethanol affords a novel two‐dimensional organotin network structure compound 1, which is an unusual network containing dinuclear 18‐membered and tetranuclear 26‐membered organotin macrocycles. The compound has been characterized by elemental analysis, IR, and ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. Furthermore, we have also characterized the compound by X‐ray crystallography.     

Extension of N‐Heteroacenes through a Four‐Membered Ring

The synthesis of novel π‐extended N‐heteroacenes, which have a large tetraazaacene subunit and a quinoxaline subunit connected through a four‐membered ring, is reported. They were studied with experimental and computational methods in comparison to the corresponding tetraazaacenes. As found from the DFT calculation, the four‐membered ring is a better linker than a five‐membered ring or a C?C single bond to extend N‐heteroacenes for a new design of n‐type semiconductors in terms of the spatial delocalization and energy level of LUMO as well as the reorganization energy. In solution‐processed thin film transistors, the π‐extended N‐heteroacenes are found to function as n‐type semiconductors with field effect mobility of up to 0.02 cm² V^?1 s^?1 under ambient conditions.     

Synthesis of a Six‐Membered‐Ring (2R)‐10a‐Homobornane‐10a,2‐sultam and Structural Comparison with Oppolzer's,Lang's,and King's Sultams

The new six‐membered‐ring (2R)‐10a‐homobornane‐10a,2‐sultam (−)‐ 3a was synthesized and its X‐ray structural analysis was compared with that of the novel structure of the five‐membered‐ring (2R)‐bornane‐10,2‐sultam analogues (−)‐ 1a , b as well as with that already published for the six‐membered‐ring trans‐decalin‐like sultam 4a . Based on DN** density‐function calculations and X‐ray crystallographic studies of the N‐methylated analogues (−)‐ 1e and 4b and by comparing with the conformation of the N‐fluoro derivatives (−)‐ 1c and (+)‐ 1d , the anomeric stabilization was estimated to be smaller than the 2.0–2.5 kcal/mol earlier suggested. The direction of pyramidalization is rationalized in terms of H‐bond and steric and electronic interactions and extended to the known toluenesultam derivatives 10a – c .     

Excited State Photoreaction between the Indole Side Chain of Tryptophan and Halocompounds Generates New Fluorophores and Unique Modifications

Photoreaction of indole containing compounds with chloroform and other trichlorocompounds generates products with redshifted fluorescence. In proteins, this reaction can be used for the fluorescent detection of proteins. Little characterization of products generated through the photochemical reaction of indoles with halocompounds has been done, yet is fundamental for the development of other fluorophores, protein labeling agents, and bioactive indole derivatives. Here, we have characterized which isomers form in the photoreaction between tryptophan and chloroform using ¹H‐NMR of tryptophan and methylated derivatives to reveal that the two major products that are formed result from modification at the 4‐ and 6‐carbon positions of the indole ring. Reaction at position 6 generates 6‐formyl tryptophan and the reaction at position 4 generates an imine because the formyl derivative that is initially formed reacts further with the tryptophan amine group. The spectroscopic properties and product molecular weights of photoproducts formed from photoreaction of tryptophan with other trihalo and monohalocompounds are also determined. The indole ring of tryptophan can be modified with various additions from halocompounds, including the addition of labels to the indole ring via methylene groups. This opens possibilities for generating novel tryptophan based fluorophores and protein labeling strategies using this photochemistry.     

Ringerweiterungsreaktionen von N-(2-Aminoäthyl)-, N-(4-Aminobutyl)-, N-(6-Amino-4-aza-hexyl)- und N-(8-Amino-4-aza-octyl)-lactamen. 7. Mitteilung über Umamidierungsreaktionen

Ring Enlargement Reactions of N -(2-Aminoethyl)- , N -(4-Aminobutyl)- , N -(6-Amino-4-aza-hexyl)- and N -(8-Amino-4-aza-octyl)-lactames The N-aminoalkyl-lactams 1 , 3 , 4 , 10 (Scheme 2) and 13 (Scheme 3) have been synthesized. In the presence of KAPA (potassium 3-aminopropylamide in 1,3-propanediamine) 1 is stable, whereas 3 , 4 and 10 rearrange under ring enlargement to 5 , 8 and 11 , respectively. The 4-aminobutyl derivate 13 rearranges in a fast reaction to 14 ; after a longer reaction time the 22membered ring 16 and the ring opened product 18 are formed. Hence it may be concluded that the 7membered lactam ring is more stable than the 10membered one, and the 11membered lactam ring is more stable than the 8 membered one. Moreover, the 5- and 6 membered ring intermediates of these transamidation reactions are prefered to the 7membered ring intermediates (cf. [10]).     

C,O‐Chelated BINOL/Gold(III) Complexes: Synthesis and Catalysis with Tunable Product Profiles

Unprecedented stable BINOL/gold(III) complexes, adopting a novel C,O‐chelation mode, were synthesized by a modular approach through combination of 1,1′‐binaphthalene‐2,2′‐diols (BINOLs) and cyclometalated gold(III) dichloride complexes [(C^N)AuCl₂]. X‐ray crystallographic analysis revealed that the bidentate BINOL ligands tautomerized and bonded to the Au^III atom through C,O‐chelation to form a five‐membered ring instead of the conventional O,O′‐chelation giving a seven‐membered ring. These gold(III) complexes catalyzed acetalization/cycloisomerization and carboalkoxylation of ortho ‐alkynylbenzaldehydes with trialkyl orthoformates.