Ferrocenophanes with Interannular Nitrogen–Gallium Bridges. 1,3,2‐Diazagalla‐[3]Ferrocenophanes and an 1‐Aza‐3‐Azonia‐2‐Gallata‐[3]Ferrocenophane. Synthesis and Structure

1,1′‐Bis(trimethylsilylamino)ferrocene reacts with trimethyl‐ and triethylgallium to give the μ‐[ferrocene‐1,1′‐diyl‐bis(trimethylsilylamido)]tetraalkyldigallanes. These were converted into the 1,3‐bis(trimethylsilyl)‐2‐alkyl‐2‐pyridine‐1,3,2‐diazagalla‐[3]ferrocenophanes, of which the ethyl derivative was characterized by X‐ray structural analysis. Treatment of gallium trichloride with N,N′‐dilithio‐1,1′‐bis(trimethylsilylamino)ferrocene affords μ‐[ferrocene‐1,1′‐diyl‐bis(trimethylsilylamido)]tetrachlorodigallane along with bis(trimethylsilyl)‐2,2‐dichloro‐1‐aza‐3‐azonia‐2‐gallata‐[3]ferrocenophane as a side product, and both were structurally characterized by X‐ray analysis. The solution‐state structures of the new gallium compounds and aspects of their molecular dynamics in solution were studied by NMR spectroscopy (¹H, ¹³C, ²⁹Si NMR).     

Total Synthesis of Bryostatin 8 Using an Organosilane‐Based Strategy

Convergent total synthesis of bryostatin 8 has been accomplished by an organosilane‐based strategy. The C ring is constructed stereoselectively through a geminal bis(silane)‐based [1,5]‐Brook rearrangement, and the B ring through geminal bis(silane)‐based Prins cyclization, thus efficiently joining the northern and southern parts of the molecule.     

Synthesis of regioisomeric 2,5‐bis‐substituted‐aza‐benzothiopyranoindazoles

The synthesis of 6‐chloro‐9‐nitro‐benzothiopyranopyridin‐5‐ones 2a, 2b and 2c has been accomplished. Chemotype 2d could not be prepared since attempts to cyclize 3‐(2‐nitro‐5‐chlorophenoxy)pyridine‐2‐carboxylic acid ( 1d ) led to the decarboxylation product 3‐(2‐nitro‐5‐chlorothiophenoxy) pyridine ( 40 ). Analogues 2a, 2b or 2c on treatment with the respectively substituted hydrazine led to the 2‐(substituted)‐5‐nitro 7, 8‐ or 9‐aza substituted chemotypes 3a‐7a, 8b , and 9c‐13c . The reduction of the nitro groups of these substrates was effected by treatment with hydrogen gas (palladium catalyst) or by stannous chloride to yield the 5‐amino chemotypes 15a‐18a, 20b and 21c‐24c , respectively. The conversion of these derivatives to the 2,5‐bis (alkylamino)‐7‐, 8‐ and 9‐aza benzothiopyranoindazoles listed in Table 3 was accomplished by direct alkylations, acylations, followed by reduction of the amido group with Red‐Al or lithium aluminum hydride, or by reductive alkylations in the presence of sodium cyanoborohydride. The removal of the protective BOC‐group was effected by treatment of the appropriate substrates with anhydrous hydrogen chloride to afford the respective hydrochloride salts listed in Table 4.     

Copper‐Catalyzed Domino Synthesis of 2‐Imino‐1H‐imidazol‐5(2H)‐ones and Quinoxalines Involving CC Bond Cleavage with a 1,3‐Dicarbonyl Unit as a Leaving Group

Although 2‐imino‐1H‐imidazol‐5(2H)‐ones have important biological activities in metabolism, their synthesis has rarely been investigated. Quinoxalines as “privileged scaffolds” in medicinal chemistry have been extensively investigated, but the development of novel and efficient synthetic methods remains very attractive. Herein, we have developed two copper‐catalyzed domino reactions for the synthesis of 2‐imino‐1H‐imidazol‐5(2H)‐ones and quinoxalines involving C?C bond‐cleavage with a 1,3‐dicarbonyl unit as a leaving group. The domino sequence for the synthesis of 2‐imino‐1H‐imidazol‐5(2H)‐ones includes aza‐Michael addition, intramolecular cyclization, C?C bond‐cleavage, 1,2‐rearrangement, and aerobic dehydrogenation reaction, whereas the domino sequence for the synthesis of quinoxalines includes aza‐Michael addition, intramolecular cyclization, elimination reaction, and C?C bond‐cleavage reaction. The two domino reactions have significant advantages including high efficiency, mild reaction conditions, and high tolerance of various functional groups.     

Synthesis of Phenanthrene Derivatives by Intramolecular Cyclization Utilizing the [1,2]‐Phospha‐Brook Rearrangement Catalyzed by a Brønsted Base

The synthesis of functionalized phenanthrene derivatives was achieved by intramolecular cyclization utilizing the [1,2]‐phospha‐Brook rearrangement under Brønsted base catalysis. Treatment of biaryl compounds having an α‐ketoester moiety and an alkyne moiety at the 2 and 2′ positions, respectively, with diisopropyl phosphite in the presence of a catalytic amount of phosphazene base P2‐tBu provides 9,10‐disubstituted phenanthrene derivatives in high yields. This reaction involves the generation of an ester enolate through an umpolung process, that is, addition of diisopropyl phosphite to a keto moiety followed by the [1,2]‐phospha‐Brook rearrangement, the intramolecular addition to an alkyne, and the [3,3] rearrangement of the allylic phosphate moiety in a consecutive fashion.     

A New Solution—phase Parallel Synthesis of 2—Alkyamino—3—aryl—5—phenylmethylene—3,5—dihydro—4H—imidazol—4—ones

Thirteen new 2-alkylaminoimidazolones(4) wre rapidly synthesized by a new solution-phase parallel synthetic method,which includes aza-Wittig reaction of iminophosphorane(1) with aromatic isocyanate to give carbodi-imide(2) and subsequent reaction of 2 with various aliphatic primary amine in a parallel fashion.The products were confirmed by ^1H NMR,MS,IR and X-ray crystallographic analysis.The unusual selectivity of the cyclization was probably due to the deometry of the guanidine intermediate.     

Metallierung und C‐C‐Kupplung von 2‐Pyridylmethylamin: Synthese und Strukturen von Methylzink‐2‐pyridylmethylamid,Tris(trimethylsilyl)methylzink‐2‐pyridylmethylamid und (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethen

Metalation and C‐C Coupling Reaction of 2‐Pyridylmethylamine: Synthesis and Structures of Methylzinc‐2‐pyridylmethylamide, Tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide and (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethene The metalation of 2‐pyridylmethylamine with dimethylzinc yields methylzinc‐2‐pyridylmethylamide ( 1 ), which shows a dimer‐trimer equilibrium in solution. Compound 1 crystallizes trimeric with a Zn₃N₃‐cycle in boat conformation. The endocyclic Zn‐N distances vary between 202 and 206 pm. Heating of this compound in toluene in the presence of dimethylzinc leads to the precipitation of zinc metal and to the formation of a few crystals of bis—[methylzinc‐2‐pyridylmethylamido]‐N, N′‐bis(methylzinc)‐2,3,5,6—tetrakis(2‐pyridyl)‐1,4‐diazacyclohexane ( 2 ). The protolysis of this solution with acetamide gives yellowish (Z)‐1‐amino‐1,2‐dipyridylethene ( 3 ) in a rather poor yield. The enamine tautomer is stabilized by N‐H···N hydrogen bridges. The demanding tris(trimethylsilyl)methyl group at the zinc atom allows the isolation of the dimeric tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide (4) ₂ in good yield. A C‐C coupling reaction of this compound with dimethylzinc is not possible.     

Regioselective Synthesis of Trichloromethyl‐Substituted Salicylates and Cyclohexenones by One‐Pot Cyclizations of 1,3‐Bis(trimethylsilyloxy)buta‐1,3‐dienes

A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl₄‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities.     

Synthesis of 2,3,3a,9a‐Tetrahydro‐1H‐cyclopenta[b]quinoxaline‐1,3,4,9‐tetracarboxylate by Cyclization of 1,5‐Bis[(trimethylsilyl)oxy]penta‐1,4‐dienes with Quinoxalines

The cyclization of 1,5‐bis[(trimethylsilyl)oxy]penta‐1,4‐dienes with quinoxalines and chloroformates afforded 2,3,3a,9a‐tetrahydro‐1H‐cyclopenta[b]quinoxaline‐1,3,4,9‐tetracarboxylate.     

Divergent Synthesis of Hydro‐γ‐Carbolines and Multisubstituted Indoles through Grob Fragmentation/Mannich Cyclization

A distinct strategy for the divergent synthesis of hydro‐γ‐carbolines and multisubstituted indoles is reported. The stereochemical outcomes and a control experiment indicate that the reactions likely proceed through Grob fragmentation/Mannich cyclization rather than a concerted aza‐pinacol rearrangement.     

Regioselective Synthesis of 5‐(2‐Cyanoethyl)‐1,1′‐biphenyl‐2‐carboxylates by Formal [3+3] Cyclocondensations of 1,3‐Bis[(trimethylsilyl)oxy]buta‐ 1,3‐dienes

5‐(2‐Cyanoethyl)‐1,1′‐biphenyl‐2‐carboxylates were prepared by regioselective formal [3+3] cyclocondensations of 1,3‐bis[(trimethylsilyl)oxy]buta‐1,3‐dienes.     

Cyclization of Zincated α‐N‐Homoallylamino Nitriles: A New Entry to Enantiopure 2,3‐Methanopyrrolidines

Stereoselective cyclization of zincated α‐N‐homoallylamino nitriles has been developed. Following treatment with lithium diisopropylamide (LDA) and transmetalation with zinc bromide, α‐N‐(1‐phenylethyl)‐N‐homoallylamino nitriles lead to 2,3‐methanopyrrolidines in moderate to good yields (up to 66 %) and excellent selectivities (up to >98:2). With substrates derived from α‐branched homoallylic amines, a stereospecific inversion of the homoallylic stereogenic center was observed. To account for this, a mechanistic rationale involving the formation of zincioiminium ions from zincated α‐amino nitriles is put forward. 2,3‐Methanopyrrolidines should then arise from a sequence involving an aza‐Cope rearrangement providing a configurationally stable (2‐azoniaallyl)zinc species that then undergoes a [3+2] cycloaddition reaction.     

Synthesis of 3‐Acyl‐4‐alkenylpyrrolidines by Platinum‐Catalyzed Hydrative Cyclization of Allenynes

A series of nitrogen‐tethered allenynes (‘5‐aza‐1,2‐dien‐7‐ynes’) 1 were transformed to the corresponding 3‐acyl‐4‐alkenylpyrrolidines 3 when treated with a catalytic amount of PtCl₂ in MeOH at 70°. Initial Pt‐promoted cyclization forms a nonclassical carbocationic intermediate. In contrast to the cycloisomerization in toluene, which produced the bicyclic cyclobutenes 2 , the intermediate is intercepted by addition of an oxygen nucleophile to achieve the formal hydrative cyclization.     

Synthesis,Molecular Structure and Coordination Chemistry of the First 1‐Aza‐3,7‐diphosphacyclooctanes

The first representatives of a novel type of cyclic bis‐phosphines, namely, 1‐aza‐3,7‐diphosphacyclooctanes ( 4 , 5 ), were synthesized by condensation of 1,3‐bis(arylphosphino)propanes ( 2 , 3 ; aryl = phenyl or mesityl), formaldehyde and 5‐aminoisophthalic acid. Only the meso isomers were obtained, in good to satisfactory yield. The cyclic bis‐phosphines readily form P,P chelate complexes ( 6 , 7 ) with [PtCl₂(cod)] (cod = 1,5‐cyclooctadiene). The bisphosphine 4 and the corresponding complex 6 are soluble in water in the presence of two equivalents of alkali metal hydroxide. The molecular structures of 1‐(meta‐dicarboxyphenyl)‐3,7‐dimesityl‐1‐aza‐3,7‐diphosphacyclooctanes ( 5 ) and cis‐{P,P‐1‐(meta‐dicarboxyphenyl)‐3,7‐diphenyl‐1‐aza‐3,7‐diphosphacyclooctane}dichloroplatinum(II) ( 6 ) are reported.     

The characteristic of photoluminescence of tris‐(7‐substituted‐8‐hydroxyquinoline) aluminum complexes and polymeric complexes

The 7‐allyl‐ and 7‐(2‐methylvinyl)‐functionalized derivatives of 8‐hydroquinoline are synthesized by Claisen rearrangement and double bond rearrangement respectively. Then 7‐allyl‐8‐hydroquinoline (C) and 7‐(2‐methylvinyl)‐8‐hydroquinoline (D) are reacted with aluminum chloride to afford the corresponding tris‐(7‐allyl‐8‐hydroxyquinoline) aluminum complex (F) and tris‐(7‐(2‐methylvinyl)‐8‐hydroxyquinoline) aluminum complex (G). The photoluminescence of complex (F) or (G), compared with that of tris‐(8‐hydroxyquinoline) aluminum complex (E), all showed a red shift in emission wavelengths in different solvents, such as chloroform, hexane and ethanol. For two substituents containing an external double bond, the 2‐methylvinyl group gives a larger red shift in the emission wavelength than the allyl group. The X‐ray crystal structure indicates that 7‐(2‐methylvinyl)‐8‐hydroxyquinoline (D) is a trans‐isomer. The styrene and 7‐allyl‐8‐hydroxyquinoline copolymer, and the styrene and 7‐(2‐methylvinyl)‐8‐hydroxyquinoline copolymer are also reported. Further reactions of the copolymer are then performed by adding aluminum(III) chloride and ligands 8‐hydroxyquinoline. The spectroscopic characteristics of these aluminum(III) polymeric complexes are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Solid‐Phase Approach for the Synthesis of 2‐Amido‐1,3,4‐oxadiazoles

A new solid‐phase approach for the synthesis of 2‐amido‐1,3,4‐oxadiazoles has been developed. In this synthesis, hydroxypentyl JandaJel polymer support was treated with excess of oxalyl chloride to give resin‐bound 2‐chloro‐2‐oxoacetate, and this intermediate was then coupled with different hydrazides to give resin‐bound 2‐(N′‐acylhydrazinyl)‐2‐oxoacetate. Intramolecular dehydrative cyclization of resulting resin‐bound linear precursor followed by direct amidation using aluminum amide reagent provided 5‐substituted 1,3,4‐oxadiazoles as 2‐carboxamides. To explore the scope of this reaction sequence, we synthesized a small set of library using a combination of hydrazides and amines, and the desired products were obtained in good to high yields.     

Kristallstrukturen und spektroskopische Eigenschaften von 2λ3‐Phospha‐1, 3‐dionaten und 1, 3‐Dionaten des Calciums ‐ ein Vergleich am Beispiel der 1, 3‐Diphenyl‐ und 1, 3‐Di(tert‐butyl)‐Derivate

Crystal Structures and Spectroscopic Properties of 2λ³‐Phospha‐1, 3‐dionates and 1, 3‐Dionates of Calcium ‐ Comparative Studies on the 1, 3‐Diphenyl and 1, 3‐Di(tert‐butyl) Derivatives A hydrogen‐metal exchange between dibenzoylphosphane and calcium carbide in tetrahydrofuran (THF) followed by addition of the ligand 1, 3, 5‐trimethyl‐1, 3, 5‐triazinane (TMTA) furnishes the binuclear complex bis[(tmta‐N, N′, N″)calcium bis(dibenzoylphosphanide)] ( 1a ) co‐crystallizing with benzene. Similarly, reaction of bis(2, 2‐dimethylpropionyl)phosphane with bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in 1, 2‐dimethoxyethane (DME) gives bis(dme‐O, O′)calcium bis[bis(2, 2‐dimethylpropionyl)phosphanide] ( 1b ) in high yield. The carbon analogues 1, 3‐diphenylpropane‐1, 3‐dione (dibenzoylmethane) or 2, 2, 6, 6‐tetramethylheptane‐3, 5‐dione (dipivaloylmethane) and bis(thf‐O)calcium bis[tris(trimethylsilylmethyl)zincate] in DME afford bis(dme‐O, O′)calcium bis(dibenzoylmethanide) ( 2a ) and the binuclear complex (μ‐dme‐O, O′)bis[(dme‐O, O′)calcium bis(dipivaloylmethanide)] ( 2b ), respectively. Dialkylzinc formed during the metalation reaction shows no reactivity towards the 1, 3‐dionates 2a and 2b . Finally, from the reaction of the unsymmetrically substituted ligand 2‐(methoxycarbonyl)cyclopentanone and bis(thf‐O)calcium bis[bis(trimethylsilyl)amide] in toluene, the trinuclear complex 3 is obtained, co‐crystallizing with THF. The β‐ketoester anion bridges solely via the cyclopentanone unit.     

Synthesis of 2,5‐bis‐arylpyridines by [4 + 2] cycloaddition of 1,4‐bis aryl‐2‐aza‐1,3‐butadienes with electron‐poor dienophiles

Tetrahydropyridines 4a, 4b, 4c and pyridines 7a, 7b, 7c, 9a, 9b, 9c were synthesized by a [4 + 2] cycloaddition between 1,4‐bis aryl‐2‐aza‐1,3‐butadienes and electron‐poor dienophiles. Dimeric cycloadducts 6a, 6b, 6c , were also isolated indicating a competition between the expected Hetero Diels‐Alder and a dimerization process.     

One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O

A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr₂·2Et₂O as catalyst.     

Efficient Preparation of 2, 2′‐Disubstituted‐3, 3′‐(1, 4‐phenylene)bis‐thienopyrimidin‐4‐ones Based on an aza‐Wittig Reaction

Tandem aza‐Wittig reaction of iminophosphorane with 1, 4‐phenylene diisocyanate followed by intramolecular heteroconjugate addition annulation after addition of a nucleophilic reagent (amine, phenol, and alcohol), in the presence of catalytic K₂CO₃ or NaOR, gives selectively the functionalized substituted 2, 2′‐di(alkylamino, aryloxy)‐3, 3′‐(1, 4‐phenylene)bis(thieno[3, 2‐d]pyrimidin‐4(3H)‐ones) and 2, 2′‐di(alkylamino or alkoxy)‐3, 3′‐(1, 4‐phenylene)bis(3, 5, 6, 7‐tetrahydro‐4H‐cyclopenta[4, 5]thieno[2, 3‐d]pyrimidin‐4‐ones).