Phosphanchalkogenide und ihre Metallkomplexe. V. Derivate von [2.2]Paracyclophanylphosphanena

The known compound diphenyl([2.2]paracyclophanyl)phosphane 1 reacted smoothly with elemental sulfur or selenium to give the phosphane chalcogenides 3 and 4. The corresponding chlorido- or bromido-gold(I) complexes were however not obtained by the usual reaction with (tht)AuCl or (tht)AuBr. For the latter, direct oxidation of the reaction mixture with elemental bromine led to small quantities of {(PCP)PPh2Br}+ [AuBr4]− 5 (PCP = [2.2]paracyclophanyl). Attempts to obtain the alkyl phosphane di-isopropyl([2.2]paracyclophanyl)phosphane 2 were at first unsuccessful because of contamination by the phosphonium derivatives [ i Pr2(PCP)PH]+X− (X = Cl 6, X = Br 7), but the mixture was found to react with elemental sulfur or selenium to give the phosphane chalcogenides 8 and 9. The gold(I) complexes (PCP) i Pr2PEAuX [E = S, X = Cl (10), Br (11); E = Se, X = Cl (12), Br (13)] were obtained by the reactions of 8 and 9 with (tht)AuX. The chlorido complexes 10 and 12 were oxidized by PhICl2 to the gold(III) complexes (PCP) i Pr2PEAuCl3 14 (E = S) and 15 (E = Se). An excess of PhICl2 led to the fully oxidized compound {(PCP) i Pr2PSeCl}+[AuCl4]− 16. The bromido complexes 11 and 13 were oxidized by elemental bromine to (PCP) i Pr2PEAuBr3 17 (E = S) und 18 (E = Se), the latter however with a poor yield. Further oxidation was not achieved. The reactions of the chalcogenides 3, 4, 8 and 9 with elemental iodine led to the products 19, 20, 21 (1:1 adducts) and 22 (1:1 adduct with additional disordered diiodine), respectively.

Synthesis, structure, and first reactions of a new class of thiacyclophanes

In our effort to prepare [m.n]cyclophanes carrying functional groups in their molecular bridges, the thiacyclophanes 14, 19, 20, and 21 have been prepared by simple routes from the pseudo-gem dibromide 10a and the corresponding bis-thiol 10b. The triply-bridged bis-thia-cyclophanes 14, and 19-21 were characterized by their spectroscopic data as well as by X-ray structural analyses. The meta-isomer 20 was oxidized to the bis-sulfone 23, which on flash vacuum pyrolysis (FVP) yielded a product mixture presumably containing the hydrocarbon 26 with a cleaved molecular bridge. Subjecting 23 to Ramberg-Bäcklund conditions (CCl4, NaOH, phase transfer catalysis) provided the chloride 24 in poor yield (9%), a [2.2]paracyclophane in which the new molecular bridge is fully conjugated.

(Hetero)aromatics from dienynes, enediynes and enyne–allenes

Recent advances in the synthesis of (hetero)aromatics starting from polyenes, such as dienynes, enediynes and enyne–allenes, are discussed.

Cyclophanes, Part 73: diastereoselective dimerization of an α,β-unsaturated ketone. Structure of all-trans-1,3-dibenzoyl-2,4-di([2.2]paracyclophan-4-yl)cyclobutane

The dimerization of an α,β-unsaturated ketone led to a product that consists of a single diastereomer with all-trans configuration, as shown by an X-ray structure investigation. We postulate that the steric bulk of the 4-[2.2]paracyclophanyl substituent is responsible for the diastereoselectivity. The central cyclobutane ring is puckered, with a fold angle of 27.9(1)°. The cyclophane units show the usual distortions associated with the bridge strain.