1,2‐Dithioquadratato‐ und 1,2‐Dithiooxalatoindate(III)

Indium(III) chloride forms in water with potassium 1,2‐dithiooxalate (dto) and potassium 1,2‐dithiosquarate (dtsq) stable coordination compounds. Due to the higher bridging ability of the 1,2‐dithiooxalate ligand in all cases only thiooxalate bridged binuclear complexes were found. From 1,2‐dithioquadratate with an identical donor atom set mononuclear trischelates could be isolated. Five crystalline complexes, (BzlMe₃N)₄[(dto)₂In(dto)In(dto)₂] ( 1 ), (BzlPh₃P)₄[(dto)₂In(dto)In(dto)₂] ( 2 ), (BzlMe₃N)₃[In(dtsq)₃] ( 3 ), (Bu₄N)₃[In(dtsq)₃] ( 4 ) and (Ph₄P)[In(dtsq)₂(DMF)₂] ( 5 ), have been isolated and characterized by X‐ray analyses. Due to the type of the complex and the cations involved these compounds crystallize in different space groups with the following parameters: 1 , monoclinic in P2₁/c with a = 14.4035(5) Å, b = 10.8141(5) Å, c = 23.3698(9) Å, β = 124.664(2)°, and Z = 2; 2 , triclinic in P with a = 11.3872(7) Å, b = 13.6669(9) Å, c = 17.4296(10) Å, α = 88.883(5)°, β = 96.763(1)°, γ = 74.587(5)°, and Z = 1; 3 , hexagonal in R3 with a = 20.6501(16) Å, b = 20.6501(16) Å, c = 19.0706(13) Å and Z = 6; 4 , monoclinic in P2₁/c with a = 22.7650(15) Å, b = 20.4656(10) Å, c = 14.4770(9) Å, β = 101.095(5)°, and Z = 4; 5 , triclinic in P with a = 9.2227(6) Å, b = 15.3876(9) Å, c = 15.5298(9) Å, α = 110.526(1)°, β = 100.138(1)°, γ = 101.003(1)°, and Z = 2.     

Halogen bonding in 1,2‐dibromo‐4,5‐dimethoxybenzene and 1,2‐diiodo‐4,5‐dimethoxybenzene

An interesting case of `halogen‐bonding‐promoted' crystal structure architecture is presented. The two title compounds, C₈H₈Br₂O₂ and C₈H₈I₂O₂, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen‐bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a π‐bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C—Br...Br—C links and with no C—Br...O/N interactions present. In the diiodo structure, instead, the C—I...O synthon prevails, defining linear chains, in turn interlinked by C—I...I—C interactions.     

1,2‐Dinitroguanidine

The title compound, CH₃N₅O₄, is almost planar, and the conformation is fixed by two intramolecular N—H⋯O hydrogen bonds. Owing to the delocalization of π‐electron density over the whole mol­ecule, there is through‐conjugation, with the C—N, N—N and N—O bond lengths having values intermediate between those typical for the corresponding single and double bonds.     

Accessing 1,2‐Substituted Cyclobutanes through 1,2‐Azaborine Photoisomerization

We provide a seminal example of the utility of the 1,2‐azaborine motif as a 4C+1N+1B synthon in organic synthesis. Specifically, conditions for the practically scalable photoisomerization of 1,2‐azaborine in a flow reactor are reported that furnish aminoborylated cyclobutane derivatives. The C?B bonds could also be functionalized to furnish a diverse set of highly substituted cyclobutanes.     

1,2‐Ph2‐9‐I‐1,2‐closo‐C2B10H9

The title compound, 9‐iodo‐1,2‐di­phenyl‐1,2‐dicarba‐closo‐dodecaborane(9), C₁₄H₁₉B₁₀I, has the expected pseudo‐icosahedral cluster geometry, with a cage C—C distance of 1.724 (4) Å, comparable to that in the non‐iodinated parent. However, the twist angles, θ, of the phenyl rings are 2.1 (6) and 27.6 (5)°, the latter being unusually large.     

The complex packing pattern of cis‐1,2‐dimethylcyclobutane‐1,2‐diol

cis‐1,2‐Dimethylcyclobutane‐1,2‐diol, C₆H₁₂O₂, crystallizes with five molecules in the asymmetric unit. Of these, two molecules are the building blocks of columns with a complex hydrogen‐bonding pattern in their hydrophilic core. The walls of the columns are formed by the lipophilic parts of the molecules. The remaining three molecules of the asymmetric unit build columns with a less complex hydrogen‐bonding system. In terms of co‐operativity, the most significant feature is the formation of homodromic rings of six hydroxy functions.     

1,2‐Bis­(methylsulfanyl)‐1,2‐dicarba‐closo‐dodecaborane(12)

In the title compound, 1,2‐(SCH₃)₂‐1,2‐closo‐C₂B₁₀H₁₀ or C₄H₁₆B₁₀S₂, the methylsulfanyl groups are bonded to the C atoms of the 1,2‐dicarba‐closo‐dodecaborane cage. The C_cage—C_cage distance is 1.8033 (18) Å and the S—C_cage—C_cage—S torsion angle is 1.07 (13)°. The C_cage—C_cage distance is compared with those in other 1,2‐dicarba‐closo‐dodecaborane derivatives.     

Green multicomponent synthesis of 1,2‐dihydro‐pyrimido[1,2‐a]‐benzimidazole‐3‐carbonitrile

1,2‐dihydro‐pyrimido[1,2‐a]benzimidazole‐3‐carbonitrile derivatives were synthesized via the three‐component reaction of aldehyde, malonodinitrile and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.     

Crystal engineering with heteroboranes. II. 1,2‐Di­carboxy‐1,2‐dicarba‐closo‐dodecaborane(12) ethanol hemisolvate

The title compound, 1,2‐(COOH)₂‐1,2‐closo‐C₂B₁₀H₁₀·0.5C₂H₆O or C₄H₁₂B₁₀O₄·0.5C₂H₆O, forms a tetramer by incorporating ethanol (solvent) mol­ecules through hydrogen bonding. Two eight‐membered rings [graph set R(8)] are formed by hydrogen bonding between two carboxyl­ic acid groups, whereas two ten‐membered rings [R(10)] are formed by hydrogen bonding between two carboxyl­ic acid groups and the OH group of an ethanol mol­ecule (solvent). Two crystallographically independent tetramers are present in the crystal structure.     

Fused 1,2‐Dithioles. Part VII

The 1,2‐dithiolosultam derivative 14 was obtained from the (α‐bromoalkylidene)propenesultam derivative 9 (Scheme 1). Regioselective cleavage of the two ester groups (→ 1b or 2b ) allowed the preparation of derivatives with different substituents at C(3) in the dithiole ring (see 27 and 28 ) as well as at C(6) in the isothiazole ring (see 17 – 21 ; Scheme 2). Curtius rearrangement of the 6‐carbonyl azide 21 in Ac₂O afforded the 6‐acetamide 22 , and saponification and decarboxylation of the latter yielded ‘sulfothiolutin’ ( 30 ). Hydride reductions of two of the bicyclic sultams resulted in ring opening of the sultam ring and loss of the sulfonyl group. Thus the reduction of the dithiolosultam derivative 14 yielded the alkylidenethiotetronic acid derivative 33 (tetronic acid=furan‐2,4(3H,4H)‐dione), and the lactam‐sultam derivative 10 gave the alkylidenetetramic acid derivative 35 (tetramic acid=1,5‐dihydro‐4‐hydroxy‐2H‐pyrrol‐2‐one) (Scheme 3). Some of the new compounds ( 14, 22, 26 , and 30 ) exhibited antimycobacterial activity. The oxidative addition of 1 equiv. of [Pt(η²‐C₂H₄)L₂] ( 36a , L=PPh₃; 36b , L=1/2 dppf; 36c , L=1/2 (R,R)‐diop) into the S? S bond of 14 led to the cis‐(dithiolato)platinum(II) complexes 37a – c . (dppf=1,1′‐bis(diphenylphosphino)ferrocene; (R,R)‐diop={[(4R,5R)‐2,2‐demithyl‐1,3‐dioxolane‐4,5‐diyl]bis(methylene)}bis[diphenylphosphine]).     

Mechanistic Investigations on the Photoisomerization Reactions of 1,2‐Dihydro‐1,2‐Azaborine

The mechanisms of the photochemical isomerization reactions were investigated theoretically by using a model system of 1,2‐dihydro‐1,2‐azaborine with the CAS(6,6)/6‐311G(d,p) and MP2‐CAS‐(6,6)/6‐311++G(3df,3pd)//CAS(6,6)/6‐311G(d,p) methods. Three reaction pathways, which lead to three kinds of photoisomers, have been examined. The structures of the conical intersections, which play a decisive role in such photorearrangements, were obtained. The thermal (or dark) reactions of the reactant species have also been examined by using the same level of theory to assist in providing a qualitative explanation of the reaction pathways. The model investigations suggest that the preferred reaction route for 1,2‐dihydro‐1,2‐azaborine, which leads to the Dewar 1,2‐dihydro‐1,2‐azaborine photoproduct, is as follows: reactant→Franck–Condon region→conical intersection→photoproduct. The results obtained allow a number of predictions to be made.     

5‐phosphorylated 1,2‐disubstituted imidazoles

1,2‐Disubstituted imidazoles react with phosphorus(III) halides in pyridine regioselectively at position 5. The reaction proceeds the more readily, the higher the electron‐donating ability of the 2‐substituent in the starting imidazole. Hitherto unknown dihalo(imidazol‐5‐yl)phosphines have been obtained, and their properties have been studied. Also synthetic methods for the preparation of various monohalo(organyl)(imidazolyl)phosphines have been developed. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:289–308, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20550     

4‐Phosphorylated 1,2‐disubstituted imidazoles

4‐Selenophosphoryl‐1,2‐disubstituted imidazoles have been obtained by thermal decomposition of methyl 5‐(diamidoselenophosphoryl)imidazolium chlorides. The position of selenophosphoryl group in the imidazole ring was proved by ¹H, ¹³C NMR spectroscopy, and X‐ray analysis. Previously unknown diamido‐ and dichloro(imidazol‐4‐yl)‐ phosphonites were synthesized, and differences in their reactivity compared to analogous 5‐phosphorylated imidazoles are shown. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:103–118, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20584     

Elucidation of π‐Conjugation Modes in Diarene‐Fused 1,2‐Dihydro‐1,2‐diborin Dianions

A series of diarene‐fused 1,2‐dihydro‐1,2‐diborins were prepared as a new B? B‐bond‐embedded polycyclic π‐electron system. The reduction of these compounds with metals produced their corresponding dianions, the π‐conjugation modes of which varied from 6π‐conjugation within the central 1,2‐diborin skeleton to 14π peripheral conjugation over the tricyclic skeleton, depending on the nature of the reduced biaryl framework. Moreover, the countercation to the dianions had a significant effect on the absorption spectra, with a dramatic color change from yellow to deep blue, depending on the distance between the tricyclic dianion skeleton and the countercation.