A convenient synthesis of a novel fused tetracyclic heterocoumarin

New tetracyclic 6H‐[1]benzopyrano[3,4‐e]pyrazolo[1,5‐a]pyrimidin‐6‐ones ( 4a‐e ) have been synthesized through the condensation under acidic conditions of [1]benzopyrano[4,3‐c][1,5]‐benzodiazepin‐7(8H)‐one ( 1 ) and a series of 3,4‐disubsituted 5‐amino‐1H‐pyrazoles 3a‐e .     

Synthesis and ring transformation of novel tetracyclic fused as-triazines

Summary Eight new tetracyclic fused as-triazines (4–6,8,11–13, and15) have been synthesized by conversion and subsequent ring transformation of 1,2-diaminoisoquinolinium (2) and -quinolinium salts (9) with 4-benzoyl-5-phenylfuran-2,3-dione (1). Selective alkylations of the new products revealed that these reactions are governed mainly by the electronic density of the lone pairs as well as by steric effects.Dedicated to em. Univ. Prof. Dr. E. Ziegler on the occasion of his 80th birthday     

A novel synthetic route to fused propenochlorin and benzochlorin photodynamic therapy probes

Reaction of meso-(2-formylvinyl)octaethylporphyrin with (CH3)3SiCN-Cu(OTf)2 produced unexpected 10(3)-trimethylsiloxyl and 10(3)-hydroxyl fused propenochlorins which, in H2SO4, underwent subsequent migration of the 8-ethyl group to the 10(3)-position of the exocyclic benzene ring to form a novel benzochlorin.     

Facile synthesis of some novel triazolo[3,4-b]thiadiazines and triazolo[4,3-b]tetrazines

4-Amino-5-ethyl-4H-1,2,4-triazole-3-thiol was used as a key intermediate for the synthesis of triazolo[3,4-b][1,3,4]thiadiazines, triazolo[4,3-b][1,2,4,5]tetrazines and Schiff’s base via reactions with various hydrazonoyl halides and salicyaldehyde, respectively. Moreover triazolyl-N-N′-triazole derivatives were prepared from reaction of Schiff’s base with various hydrazonoyl halides. The structures of all the newly synthesized heterocyclic compounds were established by considering elemental analysis and spectral data.     

A novel route to meta-aminobenzotrifluoride

Product patterns can be altered in reactions of $\text{m}$-nitrobenzotrichloride [VI] with [AHF]_x·NH₄F complex. Side-chain fluorination predominates under ‘mild’ conditions. In contrast. ‘forcing’ conditions affected unexpected $\text{in}$-$\text{situ}$ fluorination-reduction to give $\text{m}$-aminobenzotrifluoride [V] in high yield [75%] and purity [99.6%]. $\text{in}$-$\text{situ}$ reduction is probably initiated by a combination of iron from the stainless steel autoclave and trace amounts of moisture. The transformation of [VI] to [V] represents another type of $\text{in}$-$\text{situ}$ fluorination-reduction nitroaromatics, e.g. nitrobenzene [VII] to $\text{p}$-fluoroaniline [VIII]. $\text{o}$-Nitrobenzotrichloride [XI] degraded under ‘forcing’ conditions with [AHF]_x·NH₄F.     

A novel route to pH oscillators

The formaldehyde–sulfite reaction is an acid to alkali clock reaction in batch, which displays complex behaviour in a flow reactor. Current published mechanisms do not account for the behaviour in an open system. In this Letter, we construct a minimal model based on this system and demonstrate that a base-catalysed rate-determining step coupled with an appropriate OH⁻ consuming reaction can result in bistability and oscillations. The model may provide a method for the design of organic-based pH oscillators.     

A programmed polymer folding: click and clip construction of doubly fused tricyclic and triply fused tetracyclic polymer topologies

A tandem alkyne-azide addition, i.e., click, and an olefin metathesis condensation, i.e., clip, reactions in conjunction with an electrostatic self-assembly and covalent fixation (ESA-CF) process, have been demonstrated as effective means to produce constructions of programmed folding of polymers having doubly fused tricyclic and triply fused tetracyclic topologies. Thus, a series of cyclic poly(tetrahydrofuran), poly(THF), precursors having an allyloxy group and an alkyne group (Ia), an allyloxy group and an azide group (Ib), and two alkyne groups (Ic) at the opposite positions was prepared by means of the ESA-CF method. The subsequent click reactions of Ia with a linear telechelic poly(THF) precursor having azide end groups (Id) and of Ib with Ic afforded a bridged dicyclic polymer (IIa) and a tandem spiro tricyclic precursor (IIb), respectively, both having two allyloxy groups at the opposite positions of the ring units. Finally, the intramolecular metathesis condensation reaction of IIa and of IIb in the presence of a Grubbs catalyst was performed to construct effectively a doubly fused tricyclic and a triply fused tetracyclic polymer topologies (III and IV), respectively.     

A novel approach to bicyclic fused cyclopentenone derivatives

A new four-step reaction sequence leading to bicyclic fused cyclopentenone derivatives starting from cyclic ketones has been developed.     

A novel synthetic approach to angularly fused tricyclopentanoids

Cationic transannular cyclisation of the type 8-5→5-5-5 provides a short, convenient access route to spiro-fused tricyclo (6.3.0.0^1,5) undecane system.     

A novel route to spin-labeled dihydrooxepines and o-benzoquinones

A reaction of a lithiated derivative of 4,4,5,5-tetramethyl-3-oxido-4,5-dihydro-1H-imidazole 1-oxyl with 3,6-di-tert-butyl-o-benzoquinone at ?80 °C predominantly gave spin-labeled dihydrooxepine via nucleophilic 1,2-addition of the paramagnetic carbanion to the CO group of the benzoquinone followed by insertion of the O atom into the ring. At lower temperatures, this reaction was accompanied by 1,4-addition of the organolithium compound to the benzoquinone followed by oxidation of the resulting adduct into spin-labeled o-benzoquinone. This ??one pot?? process is a novel approach to organic derivatives that can further be converted into di- and polyradicals combining nitronyl nitroxide and semiquinolate fragments.     

Tandem photocycloaddition-retro-mannich fragmentation of enaminones. A route to spiropyrrolines and the tetracyclic core of koumine

[reaction: see text] Intramolecular [2 + 2] photocycloaddition of beta-aminoalkylidene malonates gives transiently a cyclobutane which undergoes retro-Mannich fragmentation to a Delta(1)-pyrroline. The tandem sequence, exemplified in two series based on tryptamine and aminoethyl-1,4-cyclohexadiene, leads to a spiroindolopyrroline skeleton and to the nonindolenine portion of koumine.     

A novel route to 2,4-dianilino-substituted pyrimidines

A method is described to couple sterically-hindered electron-poor anilines to the 4-position of the pyrimidine core using a pyrimidine-2,4-bis(trifluoromethanesulfonate).     

Leucolusine, a tetracyclic alkaloid with a novel ring system incorporating an oxindole moiety and fused piperidine-tetrahydrofuran rings

A tetracyclic ring-opened oxindole alkaloid, possessing an unprecedented ring system incorporating fused piperidine-tetrahydrofuran rings, has been isolated from the Malayan species, Leuconotis griffithii. The structure was established by analysis of the spectroscopic data and a possible biogenetic pathway from an Aspidosperma precursor is presented.     

A new route to novel 10-deoxoartemisinins

A series of novel 10-deoxoartemisinin derivatives was synthesized with high regioselectivity and yields using Heck reactions from 10β-allyldeoxoartemisinin. The configuration of the double bond of the product was determined from ¹H NMR coupling constants (J_2′-3′).     

Synthesis and properties of fused tetracyclic derivatives of 1,4-naphthoquinone thioglycosides

A series of 1,4-naphthoquinone O-acetylthioglycosides have been synthesized by the condensation of fully O-acetylated derivatives of 1-thio-d-xylose, 1-thio-L-arabinose, 1-thio-d-galactose, 1-thio-d-mannose, and 1-thiomaltose with 3-chloro-2-methoxy-1,4-naphtho-quinone. Their deacetylation with MeONa/MeOH proceeded with simultaneous heterocyclization to yield linear carbohydrate-containing tetracyclic quinones. Tetracycles with trans junction of the carbohydrate and quinone rings are poorly soluble in water and organic solvents.     

A short and efficient route to novel scyphostatin analogues

[structure: see text]. Several novel scyphostatin analogues have been prepared in up to 18% yield over five steps from commercially available 4-bromoguaiacol, utilizing an organometallic addition to afford the desired syn-hydroxy-epoxides.     

Cyclo-hydrosilylation: A novel route to siloxetanes and silanones

A novel and convenient method for the apparent liquid phase generation of dimethylsilanone, Me₂SiO (D₁), based on readily obtainable reactants and employing conventional temperatures (50–150°) is reported herein. Platinum catalyzed hydrosilylation of vinyldimethylcaarbinoxydimethylsilane (I) appears to proceed by an exclusively intramolecular path to produce not only the expected 5-membered heterocyclic, 1,1,3,3-tetramethyl-2-oxa-1 silacyclopentane (V), but also the isomeric and highly unstable 4-membered siloxetane, 1,1,3,3,4-pentamethyl-2-oxa-1-silacyclobutane (IV). The intermediacy of IV is suggested by the products: i.e., 2-methyl-2-butene which is believed to arise along with Me₂SiO from fragmentation of IV; D₃ and D₄ from D₁ self-coupling; a 6-membered cyclic derived from insertion of D₁ into the Si-O bond of IV, i.e., 1,1,3,3,5,5,6-heptamethyl-2,4-dioxa-1,3-disilacyclohexane (VI); a polymer which upon alkaline cracking produces more 6-ring (VI) but little or no 5-ring (V) suggesting that the polymer arose from copolymerization of D₁, D₂, and siloxetane (IV). Compound I is also an excellent thermolytic source of D₁ as evidenced by the formation of the expected derivatives upon heating in the presence of known silanone traps.