Synthesis and rearrangement of [1,1′-bicyclobutyl]-1-ols and spiro[3.4]octan-5-ols: a general access to bicyclo[3.3.0]octenes (hexahydropentalenes)

Several new Grignard reagents based on substituted cyclobutanes have been generated and added to cyclobutanones to yield mono- to trimethylated [1,1′-bicyclobutyl]-1-ols. Mono- to trimethylated spiro[3.4]octan-5-ols have been prepared from the parent ketone via alkylation and/or addition reactions. Upon treatment with acid, all [1,1′-bicyclobutyl]-1-ols and spiro[3.4]octan-5-ols rearrange to yield a single bicyclo[3.3.0]octene.     

Condensed Isoquinolines. 14. Spirocyclic Systems Containing a Benzo[5,6][1,2,4]thiadiazino[4,3-b]isoquinoline Ring

We propose a convenient preparative method for synthesis of derivatives of novel heterospirane systems with a benzo[5,6][1,2,4]thiadiazino[4,3-b]isoquinoline ring, based on the reaction of 1-(2-bromomethylphenyl)-1-cyclopentanecarbonitrile and 4-(2-bromomethylphenyl)-3,4,5,6-tetrahydro-2H-pyran-4-carbonitrile with o-aminobenzenesulfamide.     

Synthesen und Stereochemie des 3,6,10,13-Tetrathia[6.6.1]propellans

3,6,10,13-Tetrathia[6.6.1]propellane (1) has been prepared by two independent syntheses.1 exists as an equilibrium of two conformers with C₂ and C_s symmetry, respectively. The heterocyclic rings adopt a twist-tub conformation. The multistage synthesis of1 makes also 1,5-cyclooctadiene (5) accessible, as the result of [4_s+4_s]-cycloaddition. The formation of [6.6.1]propellanes of the isomeric [6.0.6.1]dispiranes depends on the nature of the hetero atom.

     

Condensed Isoquinolines. 15. Synthesis of 5,10-Dihydro[1,2,4]triazolo[1,5-b]isoquinolines and Related Spiranes

Condensation of o-bromomethylphenylacetonitrile with arylcarbohydrazides gave, depending on the reaction conditions, 2-arylcarboxamido-1,4-dihydroisoquinoline-3(2H)-imine hydrobromides or 2-aryl-5,10-dihydro[1,2,4]triazolo[1,5-b]isoquinolines. Analogous condensation of 4-(2-bromomethylphenyl)tetrahydro-2H-pyran-4-carbonitrile and 1-(2-bromomethylphenyl)-1-cyclopentanecarbonitrile with arylcarbohydrazides gave respectively 2-aryl-2,3,5,6-tetrahydrospiro[4H-pyran-4,10'(5'H)-[1,2,4]triazolo[1,5-b]isoquinolines and 2-arylspiro[1,2,4]triazolo[1,5,b]isoquinoline-10(5'H)-1'-cyclopentanes, derivatives of new spirane heterocycles. The reaction with condensing agents of 3-imino-2,2',3,3'5',6'-hexahydrospiro[isoquinoline-4(1H),4'-4H-pyran]-2-amine and 3-imino-2,3-dihydrospiro[isoquinoline-4(1H),1'-cyclopentane]-2-amine hydrobromides, synthesized from the corresponding bromo nitriles and hydrazine, may serve as an alternative route for the synthesis of these compounds. The structure of obtained triazoloisoquinolines was established from IR, ¹H and ¹³C NMR spectra. An X-ray crystallographic study of 2-phenylspiro[1,2,4]triazolo[1,5-b]isoquinoline-10(5H),1'-cyclopentane was carried out.     

Synthesis of 2-[5-amino-2,3-dihydro-4H-imidazol-4-ylidene]malononitriles

Using the system of tetracyanoethylene, ammonium acetate and a carbonyl compound, the preparation of 2-[5-amino-2,3-dihydro-4H-imidazol-4-ylidene]malononitriles was carried out. The structures of these new dihydroimidazoles were determined by NMR experiments and by X-ray crystallography.     

Synthesis of Boronate‐Based Benzo[fg]tetracene and Benzo[hi]hexacene via Demethylative Direct Borylation

A demethylative direct borylation is reported, which was applied to the synthesis of benzo[fg]tetracenes containing boronate ester, amide, and thioester substructures. Depending on the heteroatom adjacent to boron, the molecules showed characteristic photophysical properties, molecular arrangements, and chemical stabilities. The key to the successful synthesis is the appropriate choice of the boron source and Brønsted base. The versatility of the direct borylation was demonstrated by the synthesis of a boronate‐based benzo[hi]hexacene.     

Upper rim substituted thiacalix[4]arenes

The synthesis and structure of new tetrahydroxythiacalix[4]arenes, existing in the cone conformation and possessing reactive bromide, chloromethyl or diorganylphosphoryl groups on the upper rim of the macrocycle are described. The molecular structure of tetrakis(diisopropoxyphosphorylmethyl)thiacalix[4]arene was examined by X-ray crystallography.