Janusz Baran

Synthesis and ring-opening metathesis polymerization of eight-membered unsaturated lactams and related monomers

Abstract Novel eight-membered ring unsaturated lactams were synthesized and tested as monomers for the ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The reaction of a N-protected cyclic alkeneamine was also investigated. The Grubbs’ benzylidene complexes RuCl 2 (=CHPh)(PCy 3 ) 2 or RuCl 2 (=CHPh)(PCy 3 )(IMesH 2 ) and selected ruthenium–arene species bearing either phosphine or stable Arduengo-type N -heterocyclic carbene ligands served as catalyst precursors. In most cases, isomerization of the starting materials took place and only 1-benzyl-1-aza-2-ketocyclooct-5-ene afforded a polymeric product. This polyamide was characterized by numerous analytical techniques.

Synthesis of 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane

An efficient synthesis of the title compound 14 is reported, which employs the ZnCl2/Et2O catalyzed addition of acetyl chloride (4) to 2-methyl-2-butene (5) and the [3+ + 2] cycloaddition of the 1,1,2,3-tetramethylallyl cation to 2,3-dimethyl-2-butene as key steps.

Acceleration of diels-alder reactions by remote methyl groups

The hexamethyl substituted bismethylenecyclopentane 1a is 4 to 7 times more reactive towards the acetylenic dienophiles 2 and 3 than the nonmethylated 1,2-bismethylenecyclopentane 1b. This unusual consequence of branching is explained in terms of steric and electronic effects.

X-Ray Structure of 6(E)-[2(Z)-(Hydroxyimino)-2-phenylethyIidene]- 7,7,8,8,9,9-hexamethyl-3-phenyl-1,2-oxazaspiro[4.4]non-2-ene

Abstract The X-ray crystallographic structure of the title compound, a product of a 1,3-dipolar cy cloaddition reaction of benzonitrile oxide to 3,3,4,4,5,5-hexamethyl-1,2-bis(methylene)cyclopentane, has been determined. Colourless plates crystallize in the orthorhombic space group Pbca with cell dimensions a = 13.698(2), b = 11.836(2), c = 29.157(4) Å, V= 4727.2(1.2)Å3, Z = 8, 3736 reflections, final R(F) = 0.063 and wR(F2) = 0.166. The crystals are racemic, the molecules of opposite chirality form centrosymmetric dimers via intermolecular hydro gen bonds O-H···N between their oxime groups. The molecules are highly strained and the geometrical consequences of the steric strain are discussed.