Phase-fixed double-group 3-Γ symbols. IV. Real 3-Γ symbols and coupling coefficients for the group hierarchies T* ⊃ C 3 * and T* ⊃ C 2 *

We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C ₃ ^* and T* C ₂ ^* . They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups.     

1,4-dimethyl-3,6-dioxo-1,2,4,5-tetrazin-1-IUM-5(4h)-id,a new six-membered heterocyclic betaine

The preparation, the spectroscopic characterization, the crystal structure and chemical reactions of the new six-membered heterocyclic betaine2 are reported; 2 is a representative of a possibly large group of yet unkonwn betaines of the general structure 8.     

Design of pure heterodinuclear lanthanoid cryptate complexes

Heterolanthanide complexes are difficult to synthesize owing to the similar chemistry of the lanthanide ions. Consequently, very few purely heterolanthanide complexes have been synthesized. This is despite the fact that such complexes hold interesting optical and magnetic properties. To fine-tune these properties, it is important that one can choose complexes with any given combination of lanthanides. Herein we report a synthetic procedure which yields pure heterodinuclear lanthanide cryptates LnLn*LX₃ (X = NO₃⁻ or OTf⁻) based on the cryptand H₃L = N[(CH₂)₂N CH–R–CH N–(CH₂)₂]₃N (R = m-C₆H₂OH-2-Me-5). In the synthesis the choice of counter ion and solvent proves crucial in controlling the Ln–Ln* composition. Choosing the optimal solvent and counter ion afford pure heterodinuclear complexes with any given combination of Gd(iii)–Lu(iii) including Y(iii). To demonstrate the versatility of the synthesis all dinuclear combinations of Y(iii), Gd(iii), Yb(iii) and Lu(iii) were synthesized resulting in 10 novel complexes of the form LnLn*L(OTf)₃ with LnLn* = YbGd 1, YbY 2, YbLu 3, YbYb 4, LuGd 5, LuY 6, LuLu 7, YGd 8, YY 9 and GdGd 10. Through the use of ¹H, ¹³C NMR and mass spectrometry the heterodinuclear nature of YbGd, YbY, YbLu, LuGd, LuY and YGd was confirmed. Crystal structures of LnLn*L(NO₃)₃ reveal short Ln–Ln distances of ∼3.5 Å. Using SQUID magnetometry the exchange coupling between the lanthanide ions was found to be anti-ferromagnetic for GdGd and YbYb while ferromagnetic for YbGd.

We present a synthetic strategy to prepare the first heterodinuclear lanthanide(iii) cryptate complexes. The cryptate design ensures that the complexes are stable in solution for days. The exchange coupling in YbYb, GdGd and YbGd is investigated.     

Formation of Heptaleno[1,2-c]furans and Heptaleno[1,2-c]furanones

The dehydrogenation reaction of the heptalene-4,5-dimethanols 4a and 4d , which do not undergo the double-bond-shift (DBS) process at ambient temperature, with basic MnO₂ in CH₂Cl₂ at room temperature, leads to the formation of the corresponding heptaleno[1,2-c]furans 6a and 6d , respectively, as well as to the corresponding heptaleno[1,2-c]furan-3-ones 7a and 7d , respectively (cf. Scheme 2 and 8). The formation of both product types necessarily involves a DBS process (cf. Scheme 7). The dehydrogenation reaction of the DBS isomer of 4a , i.e., 5a , with MnO₂ in CH₂Cl₂ at room temperature results, in addition to 6a and 7a , in the formation of the heptaleno[1,2-c]-furan-1-one 8a and, in small amounts, of the heptalene-4,5-dicarbaldehyde 9a (cf. Scheme 3). The benzo[a]heptalene-6,7-dimethanol 4c with a fixed position of the C?C bonds of the heptalene skeleton, on dehydrogenation with MnO₂ in CH₂Cl₂, gives only the corresponding furanone 11b (Scheme 4). By [²H₂]-labelling of the methanol function at C(7), it could be shown that the furanone formation takes place at the stage of the corresponding lactol [3-²H₂]- 15b (cf. Scheme 6). Heptalene-1,2-dimethanols 4c and 4e , which are, at room temperature, in thermal equilibrium with their corresponding DBS forms 5c and 5e , respectively, are dehydrogenated by MnO₂ in CH₂Cl₂ to give the corresponding heptaleno[1,2-c]furans 6c and 6e as well as the heptaleno[1,2-c]furan-3-ones 7c and 7e and, again, in small amounts, the heptaleno[1,2-c]furan-1-ones 8c and 8e , respectively (cf. Scheme 8). Therefore, it seems that the heptalene-1,2-dimethanols are responsible for the formation of the furan-1-ones (cf. Scheme 7). The methylenation of the furan-3-ones 7a and 7e with Tebbe's reagent leads to the formation of the 3-methyl-substituted heptaleno[1,2-c]furans 23a and 23e , respectively (cf. Scheme 9). The heptaleno[1,2-c]furans 6a, 6d , and 23a can be resolved into their antipodes on a Chiralcel OD column. The (P)-configuration is assigned to the heptaleno[1,2-c]furans showing a negative Cotton effect at ca. 320 nm in the CD spectrum in hexane (cf. Figs. 3–5 as well as Table 7). The (P)-configuration of (–)- 6a is correlated with the established (P)-configuration of the dimethanol (–)- 5a via dehydrogenation with MnO₂. The degree of twisting of the heptalene skeleton of 6 and 23 is determined by the Me-substitution pattern (cf. Table 9). The larger the heptalene gauche torsion angles are, the more hypsochromically shifted is the heptalene absorption band above 300 nm (cf. Table 7 and 8, as well as Figs. 6–9).     

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

It is shown that azulene ( 1 ) and dimethyl acetylenedicarboxylate (ADM) in a fourfold molar excess react at 200° in decalin to yield, beside the known heptalene- ( 5 ) and azulene-1,2-dicarboxylates ( 6 ), in an amount of 1.6% tetramethyl (1RS,2RS,5SR,8RS)-tetracyclo[6.2.2.2^2,50^1,5]tetradeca-3,6,9,11,13-pentaene-3,4,9,10-tetracarboxylate(‘anti’-7) as a result of a SHOMO (azulene)/LUMO(ADM)-controlled addition of ADM to the seven-membered ring of 1 followed by a Diels-Alder reaction of the so formed tricyclic intermediate 16 (cf. Scheme 3) with a second molecule of ADM. The structure of ‘anti’-7 was confirmed by an X-ray diffraction analysis. Similarly, the thermal reaction of 5,7-dimehtylazulene ( 3 ) with excess ADM in decalin at 120° led to the formation of ca. 1% of ‘anti’- 12 , the 7,12-dimethyl derivative of‘anti’-7, beside of the corresponding heptalene- 10 and azulene-1,2-dicaboxylated (cf Scheme 2). The introduction of Me groups at C(1)and C(3)of azulene ( 1 ) and its 5,7-dimethyl derivative 3 strongly enhance the thermal formation of the corresponding tetracyclic compound. Thus, 1,3-dimethylazulene ( 2 ) in the presence of a sevenfold molar excess of ADM at 200° yielded 20% of ‘anti’- 9 beside an equal amount of dimethyl 3-mehtylazulene-1,2-dicarboxylate ( 8 ;cf. Scheme 1), and 1,3,5,7-tetramethylazulene ( 4 ) with a fourfold molar excess of ADM AT 200° gave a yield of 37% of‘anti’- 15 beside small amount of the corresponding heptalene- 13 and azulene-1,2-dicarboxylates 14 (cf.Scheme 2).     

Ru-Catalyzed Heptalene Formation from Azulenes and Dimethyl Acetylenedicarboxylate

It is shown that azulenes react with dimethyl acetylenedicarboxylate (ADM) in solvents such as toluene, dioxan, or MeCN in the presence of 2 mol-% [RuH₂(PPh₃)₄] already at temperatures as low as 100° and lead to the formation of the corresponding heptalene-1,2-dicarboxylates in excellent yields (Tables 1 and 2). The Ru-catalyzed reaction of ADM with 1-(tert-butyl)-4,6,8-trimethylazulene ( 31 ) takes place even at room temperature, yielding the primary tricyclic addition product 32 and its thermal retro-Diels-Alder product dimethyl 4,6,8-trimethylazulene-1,2-dicarboxylate ( 21 ; Scheme 4). At 100° in MeCN, 32 yields 90% of 21 and only 10% of the corresponding heptalene. These observations demonstrate that [RuH₂(PPh₃)₄] catalyzes the first step of the thermal formation of heptalenes from azulenes and ADM which occurs in apolar solvents such as tetralin or decalin at temperatures > 180° (cf. Scheme 1).     

A ‘One-Pot’ Anellation Method for the Transformation of Heptalene-4,5-dicarboxylates into Benzo[a]heptalenes

It has been found that dimethyl heptalene-4,5-dicarboxylates, when treated with 4 mol-equiv. of lithiated N,N-dialkylamino methyl sulfones or methyl phenyl sulfone, followed by 4 mol-equiv. of BuLi in THF in the temperature range of ?78 to 20°, give rise to the formation of 3-[(N,N-dialkylamino)sulfonyl]- or 3-(phenylsul-fonyl)benzo[a]heptalene-2,4-diols of. (cf. Scheme 4, and Tables 2 and 3). Accompanying products are 2,4-bis{[(N,N-dialkylamino)sulfonyl]methyl}- or 2,4-bis[(phenylsulfonyl)methyl]-4,10a-dihydro-3H-heptaleno[1,10-bc]furan-3-carboxylates as mixtures of diastereoisomers of. cf. Scheme 4, and (Tables 2 and 3) which are the result of a Michael addition reaction of the lithiated methyl sulfones at C(3) of the heptalene-4,5-dicarboxylates, followed by (sulfonyl)methylation of the methoxycarbonyl group at C(5) and cyclization of. (cf. Scheme 5). It is assumed that the benzo[a]heptalene formation is due to (sulfonyl)methylation of both methoxycarbonyl groups of the heptalene-4,5-dicarboxylates of. (cf. Schemes 6 and 8). The resulting bis-enolates 35 are deprotonated further. The thus formed tris-anions 36 can then cyclize to corresponding tris-anions 37 of cyclopenta[d]heptalenes which, after loss of N,N-dialkylamido sulfite or phenyl sulfinate, undergo a ring-enlargement reaction by 1,2-C migration finally leading to the observed benzo[a]heptalenes of. (cf. Schemes 8 and 9). The structures of the new product types have been finally established by X-ray crystal-structure analyses (cf. Figs. 1 and 2 as well as Exper. Part).     

Oral malodor,assessed by closed-loop,gas chromatography,and ion-trap technology

A method is described for the analysis of volatile organic compounds in saliva and tongue coating samples. The techniue is based on an off-line preconcentration step by means of a closed-loop trapping system followed by gas chromatography-ion trap detection. With the closed-loop technique, the volatile organic compounds(VOCs) are released from the matrix and trapped on an adsorbent without interference of water. The VOCs are released from the adsorbent into the gas chromatograph by thermdesorption. After separation, identification of the compounds is performed by ion trap technology. By this technique 82 compounds could be demonstrated in saliva and tongue coating samples. The technique is also used to demonstrate the formation of volatile bacterial fermentation compounds when a protein substrate is added to tongue coating samples. It is considered a very promising tool in further research on oral malodor.     

Einige bestrahlungsexperimente mit 2, 1-Benzisothiazolen

Some Irradiation Experiments with 2, 1-Benzisothiazoles 2, 1-Benzisothiazole ( 1 ) on irradiation with a mercury high-pressure lamp in benzene/diethylamine yields, after acetylation, 2-acetylamino-benzaldehyde ( 3 ; Scheme 1). Similarly, irradiation of 3-chloro-2, 1-benzisothiazole ( 2 ) in benzene/diethylamine leads to a mixture of 3-dimethylamino-2, 1-benzisothiazole ( 6a ) and N, N-diethyl-thioanthranilamide ( 7a ; Scheme 2). Benzisothiazole 6a , on irradiation, is not transformed into 7a . On the other hand, when 2 is irradiated in methanol a mixture of 3-methoxy-2, 1-benzisothiazole ( 4a ) and methyl anthranilate ( 5a ; Scheme 2) is obtained. In this case, 4a on irradiation in methanol or ethanol also yields 5a . No exchange of the methoxy group in 4a is observed when the irradiation is performed in ethanolic solution. Thus, 2, 1-benzisothiazoles 1 , 2 and 4a react photochemically by N,S-bond cleavage and hydrogen-atom abstraction from the solvent (Scheme 3). 3-Chloro-2, 1-benzisothiazole ( 2 ) shows a second photoreaction, i.e. nucleophilic exchange of the chloro substituent by methanol or diethyl amine. The latter reaction can also be observed thermally, e.g. in boiling methanol in the presence of methoxide ions.