Synopsis In continuation of previous studies on keratin-substantive sunscreens, two series of quaternary ammonium compounds, derived from 2,4-dihydroxy and from 4-hydroxybenzophenone and containing O-alkyl and N-alkyl chains of different length were prepared and submitted to substantivity tests on wool, to microbiological tests on two bacterial and two fungal species, and to tests for allergenicity/irritation on human skin. All compounds were rapidly adsorbed by wool in aqueous solution: as expected, the maximum amounts adsorbed at equilibrium (S(max)), indicative of the skin substantivity, were greatest for the C12 N-alkyl derivatives, and showed a progressive decrease with increasing length of the N-alkyl substituent. No substantial substantivity differences were detected in four C12 quaternary derivatives, differing by the presence (or absence) of a 2-OH group in the benzophenone moiety and by the length of the O-alkyl (n= 2 or 3) side chain. When tested for antimicrobial activity, however, only the 4-hydroxybenzophenone C12 quaternary derivatives showed an order of activity comparable with that of two reference compounds. The conditions leading to a maximal antibacterial activity in the present compounds appeared to be the absence of the 2-OH group, and a shorter O-alkyl side chain. None of the new quaternary derivatives showed skin-irritant properties. The results of this investigation, while confirming the peak substantivity of C12 quaternary derivatives, indicate the possibility of dissociating, in a quaternary ammonium sunscreen, the skin substantivity from other unwanted side-effects, and offer some guidelines for the development of safer agents of this type.
Tetra-acetylethylene (I), prepared by oxidation with iodine of the dithallium(1) salt of tetra-acetylethane (11), reacts with hydrazine to give a mixture of 1,4,5,8-tetramethylpyridazino [4,5-d] pyridazine (IV) and 6-amino-1,4,5,7-tetramethylpyrrolo[3,4-d]pyridazine (V). Treatment of compound (I) with hydrochloric or hydrobromic acid yields furan derivatives, whose structures can be established by chemical and spectroscopic methods. Compound (I) gives a Diels-Alder adduct with 2,3-dimethylbutadiene.THIS work arose from attempts to synthesise 1,4,5,8tetramethylpyridazino[4,5-d]pyridazine (IV) . Pyridazines can be obtained by the reaction of hydrazine with 2,3-unsaturated 1,4-diketones; 2-4 we therefore needed to prepare t etra-acetylethylene (3,4-diacetylhex-3-ene-2,5-dione) (I).Attempts to prepare this compound from 3-bromoacetylacetone, in alkaline medium, failed. Oxidation, by iodine, of tetra-acetylethane (11), previously treated with sodium ethoxide (2 mol.), was equally unsuccessful. However, oxidation of the dithallium(1) salt of compound (11) afforded compound (I) as pale yellow needIes, m.p. 139-140'.The i.r. evidence strongly supports a centrosymmetric structure for this compound in the solid state: only two carbonyl bands (1690 and 1680 crn.-l) are observed in the double bond region. In solution a small distortion probably occurs since besides the bands at 1690 and 1703 cm.-l, the Raman modes at 1703 (C=O) and 1600 (C=C) cm.-l appear as weak bands at about the same frequencies.
tetracarbonitrile (TCBF) and (3,6-dicyano-9H-fluoren-9-ylidene)propanedinitrile (TCPF) have been synthesized starting from 9-0~0-9H-fluorene-3,6-dicarbonitrile. A 2 : 1 charge transfer complex of TCPF with NNN'N'-tetramethyl-p-phenylenediamine has been obtained, and the electrical and spectral properties investigated. Conductivity measurements performed on polycrystalline samples gave a value of the order of 0.02 R-' cm-l. These results support the ability of this new acceptor in forming charge-transfer complexes with semiconducting properties.The electrical conductivity of organic materials is generally very low. However, a new class of organic solids which exhibit high conductivity has been discovered and form the basis of the field of organic Strong molecular donors and acceptors react to form ion radical salts and charge-transfer compounds, whose optical, magnetic, and structural properties are directly related to the electronic interaction between molecule^.^ Tetracyanoquinodimethane (TCNQ) is the best molecular acceptor discovered to date; it forms organic semiconductors with a large number of cation^.^''Recently we devoted our attention to the study of the electronic and vibrational properties of 9,9'-bifluorenylidene,6-7 a highly symmetric molecule. In view of the chemical and physical properties of this material, we decided to synthesize new compounds by choosing fluorene and 9,9'-bifluorenylidene as starting compounds on which to construct functionalised electron acceptors. In this paper we report the synthesis and the study of 9,9'-bifluorenylidene-3,3',6,6'-tetracarbonitrile (TCBF) and (3,6-dicyano-9H-fluoren-9-ylidene)propanedinitrile (TCPF) which are important for the preparation of semiconducting salts. They allow for high structural symmetry and comparable dimensions of both acceptors and donors, high affinity of acceptors, and electron availability of donors. NNN'W-Tetramethyl-p-phenylenediamine (TMPD) was chosen as the donor for use in the synthesis of complexes. With TCPF it formed a charge-transfer complex showing the characteristic features of semiconducting material.
PYRIDAZINO[4,5-d]PYRIDAZIXE (111) is a heterocyclic ring of very high symmetry, which has never been prepared despite much research on polyazanaphthalene compounds.1 Recently we reported2 the synthesis of several derivatives of (111), formed by treatment of ethyl ethylene tetracarboxylate and of ethyl pyridazine-4,bdicarboxylate with hydrazine. Previously only two derivatives were actually known.33
The new substituted cyclohexane- and cyclohexene-1,3-diones 3–6 and 9, 10, respectively, have been synthesized from tetraacetylethylene 1, through a ring expansion of the cyclopentenone 2. The structures of these products, as well as some features of their tautomeric behavior, were established on the basis of chemical properties and spectroscopic data.
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