Compartmental ligands. Part 7. The reactions of 1,2-diaminobenzene and cis-1,2-diaminocyclohexane with heptane-2,4,6-trione and 1-(o-hydroxyphenyl)butane-1,3-dione. The crystal structures of 1-(o-aminophenyl)-2,6-dimethyl-4-pyridone hemihydrate and {3,3′-(cis-1,2-cyclohexanediyldi-imino)bis[1-(o-hydroxyphenyl)but-2-enonato]-(N,N′,O¹,O¹′)}copper(II)

Abstract

The reaction of Il2-diaminobenzene with heptane-2,4,6-trione yielded either the compound 2-(acetylmethyl) -4-methyl-3H-I ,5-benzodiazepine or 1 -(o-aminophenyl)-2,6-dimethyl-4-pyridone (5) depending upon the conditions used. The reaction of Il2-diaminobenzene with 1 -(0-hydroxyphenyl) -butane-I ,3-dione yielded a diazepine. In contrast the reaction of cis-I ,2-diaminocyclohexane with heptane-2,4,6-trione yielded a tetramine macrocyclic compound, and with 1 -(0-hydroxyphenyl) butane-I ,3-dione afforded the compartmental Schiff base 3,3'-(cis-1 ,2-cyclohexanediyldi-imino)bis[l -(o-hydroxyphenyl)but-2-enone] (1 0). The metal-complexing properties of this ligand are reported. Three-dimensional X-ray crystal-structure analyses have been carried out on compound (5) and on the mononuclear copper(ii) derivative of (lo), i.e. (12). Compound (5) has Z = 8 in a monoclinic cell with space group P2,/c, and dimensions a = 14.984(1), b = 7.475(3), c = 21.173(1) A, and P = 98.71JI)'; R = 0.0388 for 2 392 reflections. Complex (12) has Z = 4 in a triclinic cell with space group PI, and dimensions a = 13.143(8), b = 14.279(8), c = 14.289(14) A, a = 67.36(6), p = 71.18 (7), and y = 91.36(5)"; R = 0.0651 for 2 985 reflections. The structure shows the copper(ii) to occupy the inner (N202) co-ordination site in an environment with a marked (ca. 1 4') tetrahedral twist.The reaction of P-diketones with a,o-diamines leads to a large range of products depending on the experimental conditions used.2 In reaction (i) (Scheme) it is found that neutral and mildly alkaline media favour bis(oxoenamine) formation whereas reactions at pH < 6 and pH > 10 favour diazepine formation. In reaction (ii) (Scheme) it is the anil that is stabilised if R = R' = R2 = CH3 because of the steric hindrance of the vicinal methyl groups. With P-triketones extra degrees of complexity are offered and it has been found that reactions of heptane-2,4,6-trione with various stoicheiometric proportions of 1,2-diaminoethane (and also 1,2-and 1,3-diaminopropane) give the macrocyclic Schiff bases corresponding to (l).3 With the related unsymmetrical triketones, 1 -phenylhexane-1,3,5-trione and 7,7-dimethyloctane-2,4,6-trione, acyclic Schiff bases such as (2) are formed.4~~ These reactions parallel the behaviour of the corresponding P-diketones in which condensation occurs at the carbonyl group adjacent to the methyl The reaction of pentane-2,4-dione with 1,2-diaminobenzene has been shown to give the diazepine (3).* Using similar reaction conditions, 1,2-diaminobenzene in an ethanolethanoic acid mixture was treated with heptane-2,4,6-trione to give a red compound, subsequently identified as the diazepine (4). However if the reaction was carried out by adding the components in reverse order, followed by pouring into water and refrigerating, then two products were recovered, (4) together with a white crystalline compound identified as the pyridone (5).

Mixtures obtained by reacting trans-(±)-1,2-diaminocyclohexane with acetylacetone in the presence of simple cobalt(II) salts

“…In conclusion, it is seen that in the absence of a metal ion, trans-( 9 )DCH reacts with acacH (1:2.5 mole ratio) to form the bisoxoenamine condensation product, boe (1 − ligands (no DCH and no DCH/acacH condensation products) and the metal centres are Co(III) and Co(II), respectively. Both acac − and neutral (9 )DCH ligands chelate to the oxidised Co(III) centre in 9.…”

“…1 For example, in Scheme 1, formation of the bisoxoenamine (a) is favoured in the pH range 6 -10, whereas diazepine (b) production occurs under either more acidic or more alkaline conditions. In Scheme 2 the anil (a) is stabilized when R=CH 3 because of steric effects.…”

“…Bailey et al [1] noted that with Schiff bases derived from trans-DCH the bite sizes limit complex formation because of the steric constraint introduced by an unfavourable overlap between the cyclohexane bridge protons (on C3 and C4) and the methyl groups adjacent to the nitrogen of the Schiff base. With this in mind these workers used cis-DCH in preference to the trans isomer for the preparation of compartmental Schiff base ligands from b-triketones.…”

“…Condensation reactions involving b-diketones and a,v-diamines can give a range of products depending on the experimental conditions [1,2]. 1 For example, in Scheme 1, formation of the bisoxoenamine (a) is favoured in the pH range 6 -10, whereas diazepine (b) production occurs under either more acidic or more alkaline conditions.…”

Synthesis of novel polycarbonyl Schiff bases by ring-opening reaction of ethyl 5-acyl-4-pyrone-2-carboxylates with primary mono- and diamines

“… 11 Unlike the 1,3-dicarbonyl motif, the introduction of the polycarbonyl moiety into the molecule based on 1,3,5-triketones and other open-chain polyketones has some drawback, such as side reactions (the retro-Claisen cleavage, the intramolecular cyclization), a low selectivity, and low chemical reactivity of these substrates due to the presence of the acidic protons involved in the formation of the intramolecular hydrogen bonds. 12 In the literature there are only a few examples of salen ligand synthesis based on 2,4,6-hexanetriones. 13 Using acyl-4-pyrones as highly reactive synthetic equivalents of 1,3,5-triones, which can undergo Michael reaction under the action of amines as a key stage to circumvent the above difficulties.…”