Electrophilic bromination occurs regiospecifically at the antipodal pyrrolenic ring of free-base porphyrins bearing substituents that fix the aromatic delocalization pathway; this new feature of porphyrin chemistry is not observed in the reactions of the corresponding metalloporphyrins as the pre-requisite bond fixation is only possible in free-base compounds.

A 2,3-diaminoporphyrin has been synthesised for the first time and its reaction with a-diones has been examined. Two regioselective routes to the precursor 2-amino-3-nitroporphyrins have been established. 2-Aminoporphyrins are directly nitrated on the porphyrin ring in the 3-position while 2-nitroporphyrins react with acylamide ions regioselectively at the 3-position and can be converted to the required 2-amino-3-nitroporphyrins by hydrolysis of the amide bond. 2,3-Diamino-5,10, 15,2O-tetraarylporphyrins are prepared by transfer hydrogenation of the corresponding 2-amino-3-nitroporphyrins but are relatively unstable. Electrochemical measurements show that 2,3-diaminoporphyrins are easily oxidised and this probably accounts for their instability. Condensation of the 2,3-diarninoporphyrin 29 with the a-diones benzil and cyclohexane-1,2-dione occurs readily and in good yield to give the ring annulated systems 31 and 32, respectively. Reaction with o-benzoquinone, however, causes decomposition of the diaminoporphyrin 29 making 'reverse' synthesis of quinoxalinoporphyrins and related polyporphyrin systems much less attractive than the alternate approach involving condensation of a porphyrin-2,3-dione with ophenylenediamine and related diamines.hrper 6/04245G

Derivatization of 5 with carbon dioxide, dimethyl disulfide, and chlorotrimethylsilane leads to formation of the expected products 8 (50%), 9a (53%), and 9b (67%), respectively, which were characterized by NMR spectroscopy and mass spectrometry ( Table 1); dimethyl sulfate affords 2-methyl-1-pentene in 68% yield. Since the two anionic centers of 5 differ in their reactivity, the reaction can also be carried out stepwise with two different electrophiles, for example, first with one equivalent of dimethyl disulfide and then with chlorotrimethylsilane. The formation of 10 (Scheme l, Table l ) in 25% yield proves that-as expected-the homoallyl position is more reactive than the vinyl position. This is further supported by the tandem reaction with methanol and chlorotrimethylsilane, which gives mainly 2-trimethyl~ilyl-l-butene['~ (33%). However, the presence of traces of 2-lithio-1-butene 11 always has to be taken into consideration, since still unreacted 3 is in part metalated by 5.that, before ring-opening occurs to give 16, the initially formed radical anion 14 reacts with a second lithium atom to give the I-lithiomethylcyclopropyllithium 15. As a cyclopropylcarbinyllithium derivative, 15 then undergoes the known['"] anionic rearrangement with ring-opening to form the primary homoallyllithium derivative 17.['11 Experimental ProcedureApproximately 10% of a solution of 3 (8.0 g, 0.15 mol) I121 in 50 mL of die-thy1 ether was added dropwise, initially at room temperature, to a suspension of lithium powder (2.5 g, 0.36 mol, 2% sodium) in 50 mL of diethyl ether, the reaction being carried out under argon. After the reaction had begun-the reaction solution turned yellow and began to reflux-the remaining solution of 3 was added at ice-bath temperature so as to avoid partial evaporation of 3 (b.p. 10°C). The reaction mixture was then stirred for 1/2 h at room temperature and the excess lithium was filtered off under inert gas. Yield: 70-75% 5 ; very stable (half-life period of decomposition, 27 d at room temperature).

Nahezu planar sind die beiden Titelverbindungen 1 und 2 im Kristall. Durch Röntgenstrukturanalyse beider Verbindungen konnten über Jahrzehnte bestehende Unsicherheiten bezüglich Synthese und Strukturzuordnung ausgeräumt werden. Bei der extrem starken und auch kinetisch aktiven Base 1 fällt der große zentrale äußere Winkel der Naphthalineinheit auf (125.4°), der einen relativ großen N ⃛N‐Abstand (272.8 pm) ermöglicht.

Contour-clamped homogeneous electric field (CHEF) gel electrophoresis has been used to study the karyotypes of a range of Saccharomyces cerevisiae yeast strains. The time required from sampling yeast cultures to CHEF analysis was achieved within six hours, making this procedure very useful in reference and quality control work in the brewing industry. Regions of the chromosome profiles were closely studied by adjusting electrophoresis conditions to increase resolution between bands. Both ale and lager strains of brewing yeasts were studied alongside haploid laboratory strains. By comparing different regions of the profiles even very closely related strains of lager yeast could be distinguished. Brewing strains consistently had significantly more chromosome bands than haploid laboratory strains. The electrophoretic karyotypes of browing yeasts were represented as groups of bands on CHEF gels which apparently comigrated with their haploid chromosomal counterparts.