Competitive pathways in the synthesis of cyclopropa[b]naphthalene

The product distribution obtained from dehydrochlorination of the benzobicycloheptene 1 is dependent on the reaction conditions. In tetrahydrofuran at high base concentration cyclopropa[b]naphthalene (2) predominates, whereas at low base concentration 6 - chlorobenzo[a]cyclohepta - 1,3,5 - triene (4) is the major product. In dimethyl sulphoxide 2 and 4 are formed in low yields, the ether 10 being the major product.     

Cycloproparenes: Approaches to cyclopropa[c]furan

Treatment of 6,6-dichloro-3-oxabicyclo[3.1.0]-hexane (7) with potassiumt-butoxide generates the ring-strained cyclopropene8 as a reactive intermediate. With 1,3-diphenylisobenzofuran compound8 is trapped as a 51 mixture of theexo- andendo-adducts11a and11b, respectively. With furan only the ring expanded vinylcarbene12 is intercepted and spirocycle13a is formed. Carbene12 is also captured by cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, and diphenylethyne to give22–25 respectively. A likely side product in these reactions is the pyran14.On leave from Petrolite Corporation, St. Louis, MO, USA.Taken in part from a lecture delivered at the International Chemical Congress of Pacific Basin Chemical Societies, Honolulu, December 1989 (Pacifichem '89); Abstract ORGN 016. A preliminary report was communicated (see ref. [13]).     

The synthesis of benzo[b]phenanthro[d]thiophenes and anthra[b]benzo[d]thiophenes

The synthesis of benzo[b]phenanthro[2, 3-d]thiophene ( 5 ), benzo[b]phenanthro[4, 3-d]thiophene ( 6 ), benzo-[b]phenanthro[2, 1-d]thiophene ( 9 ), benzo[b]phenanthro[3, 2-d]thiophene ( 14a ), anthra[1, 2-b]benzo[d]thiophene ( 24 ), anthra[2, 3-b]benzo[d]thiophene ( 29 ) and anthra[2, 1-b]benzo[d]thiophene ( 30 ) is described as well as the preparation of 13-methylbenzo[b]phenanthro[3, 2-d]thiophene ( 14b ).     

Synthesis and structure characterization of unsymmetrical oxacalix[2]benzene[2]pyrazines

The synthesis of two unsymmetrically linked oxacalix[2]benzene[2]pyrazines (1 and 2) is described. X-ray single crystal structure analysis revealed a highly distorted 1,3-alternate conformation of compound 1 (containing ortho- and meta-diphenol components) and a distorted boat conformation of compound 2 (containing meta- and para-diphenol components). Oxacalix[2]benzene[2]pyrazine containing both ortho- and para-diphenol components was not obtained via similar synthetic strategy.     

1,4-Addition of benzene to a dihydrocyclopent[a]indene diradical: synthesis and DFT study

Photochemical cyclization of compound 1, a homoenediyne (-CCC=CCH2CC-) bearing two ethynylanthracene chromophores, yields two isomeric dihydrocyclopent[a]indene ring systems, spiro-fused to the 9-position of a 9,10-dihydroanthracene moiety. Evidence of a photochemically initiated diradical cyclization pathway is proposed on the basis of (i) hydrogen abstraction from reaction with 1,4-cyclohexadiene (1,4-CHD) and (ii) the observation of 1,4-addition of benzene (solvent). The reaction was further analyzed by a complete density functional theory (DFT) study, using an unrestricted approach (UBLYP) with a 6-31G* basis set for the open-shell triplet states of the reactants, products, and diradical intermediates to model the photochemical nature of observed transformation. A mechanism detailing the observed cyclization/addition reaction is proposed.     

Acetylenchemie 11. Mitt.: Synthese und Kristallstruktur des 11-Isopropyliden-1a,10b-dihydro-1H-1,6-methanodibenzo[b,f]cyclopropa[d]azepins

Summary The synthesis of 11-isopropyliden-1a,10b-dihydro-1H-1,6-methano-dibenzo[b,f]cyclopropa[d]azepine by phase-transfer catalysed reaction of 5H-dibenzo[b, f]azepine with 2-chloro-2-methyl-3-butyne is described. The structure is confirmed by X-ray diffraction.

     

Dibenzo[d,h][1,3,6,7,2]dioxadithiasilonin: Synthesis and characterization

The reaction of 2,4-di-t-butylphenol, 4 , with sulfur monochloride gave the trithiobisphenol 5 rather than the expected dithiobisphenol 7 . The thiol 6 was obtained by the reduction of 5 with zinc under acidic conditions. The dithiobisphenol 7 was prepared by the oxidative coupling of 6 with iodine under alkaline conditions. The dibenzo[d,h][1,3,6,7,2]dioxadithiasilonin 8 was prepared by the reaction of 7 with dichlorodimethylsilane using triethylamine as an acid acceptor. No change was observed in the ¹H nmr spectrum of 8 upon cooling to ?55°, which suggests that the ΔG* for ring inversion is less than the corresponding eight-membered dibenzo[d,g][1,3,2]dioxasilocin and dibenzo[d,g][1,3,6,2]dioxathiasilocin 1 and 2 , respectively. The spectral data and elemental analysis are fully in accord with the nine-membered silonin structure.     

Synthesis of cyclopropa[c]indeno[1,2-b]quinolines through a MCR/Staudinger/aza-Wittig sequence

Spirocyclopropanes were prepared from aromatic aldehydes, 1,3-indandione and acetophenones through a halogenation/S_N2-displacement/Michael-initiated ring-closing sequence by a pyridinium-ylide-assisted multicomponent reaction, and their further use was also researched in the construction of cyclopropa[c]indeno[1,2-b]quinolines through subsequent Staudinger/aza-Wittig reactions.     

The synthesis of heterocyclic derivatives of dibenzo[a,d]cycloheptene

The synthesis of 2-amino-7,8-dihydrobenzo[1,2]cyclohepta[3,4,5-de]quinazoline ( 10 ) and 6,7-dihydrobenzo[1,2]cyclohepta[3,4,5-cd]indazole ( 5 ) is described.     

The synthesis of some benzo[d1]furo[3,2-e] [1,4] diazepin-2-ones

Reaction of 3-amino-2-benzoylbenzo[b]furan with bromoacetyl bromide followed by cyclization in methanolic ammonia gave 5-phenyl-1,3-dihydrobenzo[d′] furo[3,2-e] [1,4]diazepin-2-one, a representative of a new ring-system. The corresponding chloro substituted diazepin-2-one was similarly prepared from 3-amino-2-(4-chlorobenzoyl) benzo[b] furan. Some alkylation and thionation reactions of these diazepines have been investigated.     

Carboxylic acid functionalized ortho-linked oxacalix[2]benzene[2]pyrazine: synthesis, structure, hydrogen bond and metal directed self-assembly

Cyclooligomerization of 2,6-dichloropyrazine 4 and benzyl 2,3-dihydroxybenzoate 5 under microwave irradiation resulted in a racemic pair of ester functionalized ortho-linked oxacalix[2]benzene[2]pyrazine 6, which was further transformed to the corresponding racemic carboxylic acid functionalized ortho-linked oxacalix[2]benzene[2]pyrazine 3. Both enantiomers of 3 adopt 1,3-alternate conformations with their two carboxylic acid groups pointing to opposite directions in the solid state. Enantiomers of 3 form a step-like one-dimensional supramolecular polymer via intermolecular hydrogen bond interactions between the carboxylic acids for crystals obtained in methanol. No hydrogen bonds were formed between the carboxylic acids for crystals of 3 obtained in pyridine and aqueous guanidine solutions; instead, intermolecular hydrogen bonds between the carboxylic acid groups of 3 and pyridine, as well as guanidinium ions were formed. Under metal-mediated self-assembly conditions, the pyrazinyl nitrogen atoms in 3 interacted with transition metal ions, such as Ag(I), Cu(II) and Zn(II), and resulted in the formation of four new metal-containing supramolecular complexes. Metallomacrocycles 7, 8 and 9 were formed by reactions of 3 with Ag(I) or Cu(II) ions by bridging two ligands 3 in the equatorial region via M-N coordination bonds. A one-dimensional coordination polymer 10 was generated by reaction between ligand 3 and Zn(II) ions, and a cage-based structure is presented in 10 by bridging of the cyclophane units by Zn(2+) ions via Zn-N and Zn-O bonds.     

A naphtho[2,1-b]furan as a new fluorescent label: synthesis and spectral characterisation

A fluorescent naphthofuran was synthesised from an oxobenzopyran by alkaline ring contraction and coupled with various l-amino acids at their N-terminus or at side-chain functional groups, in order to evaluate its applicability as a fluorescent label for biomolecules and in peptide synthesis. Fluorescence data were collected for all derivatives, which were found to be moderately fluorescent and having moderate to good fluorescence quantum yields.