Reactions of [η-carboxycyclopentadiene][η-tetraphenylcyclo butadiene] cobalt with alkyl and aryl tin oxides: Synthesis, structural studies and electrochemistry of novel monomeric and dimeric [η-carboxycyclopentadiene][η-tetraphenylcyclobutadiene]cobalt based stannoxanes

Reactions of [η⁵-carboxycyclopentadienyl][η⁴-tetraphenylcyclobutadiene] cobalt, Ph₄C₄CoC₅H₄COOH (1), with (Ph₃Sn)₂O, [(n-Bu)₂SnO]_n and (Ph₂SnO)_n in refluxing toluene resulted in the formation of the monomeric compound Ph₃SnOC(O)C₅H₄CoC₄Ph₄ (2) and dimeric compounds n-Bu₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (3) and Ph₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (4), respectively. Reactions carried out in the solid state by mechanical grinding also yielded same results. Crystal structure determination and cyclic voltammetric studies of compounds 1, 2, 3 and 4 have been carried out and compared with similar ferrocene carboxylic acid derivatives. The structures and electrochemistry of these compounds are compared with analogous organotin ferrocene carboxylates. The results obtained from the reaction of 1 with alkyl and aryl tin oxides suggest that the formation of stannoxanes assemblies having more than two carboxylate units are not favored indicating that 1 is a highly sterically hindered metallocene carboxylic acid.     

Hydrogen Bonding Patterns in Trimethoprimium Cinnamate 1.52 Hydrate

Abstract  

In the title compound, [C₁₄H₁₉N₄O₃ ⁺, C₉H₅ O₂ ⁻, H₂O, O0.52] the asymmetric unit contains a protonated trimethoprim cation and a cinnamate anion and two water molecules. The crystal structure was determined by single crystal X-ray diffraction. This compound crystallized in the triclinic system; space group P−1 with the unit cell parameters a = 10.010(2) ?, b = 10.339(3) ?, c = 13.486(8) ?, α = 105.32(3)°, β = 109.88(3)°, γ = 100.89(3)°, V = 1204.6(10) ?³, Z = 2. The cinnamate group is disordered. The trimethoprim (TMP) molecule is protonated at one of the pyrimidine nitrogen atoms. The carboxylate group of the cinnamate anion interacts with the protonated pyrimidine atom N1 and the 2-amino group via a pair of N–H···O hydrogen bonds, generating the R₂²(8) ring motif. The inversion related TMP cations are paired via N–H···N hydrogen bonds. In addition to the base pairing, the O1W atom bridges the 2-amino and 4-amino groups on either side of the paired bases, resulting in a self complementary DADA array. Two inversion related TMP cations and water molecules (O1W) are linked via N–H···O and O–H···O hydrogen bonds, forming a 22 membered ring with graph-set R₄⁴(22).     

Copolymers of 2-vinyl-4,4-dimethylazlactone with styrene and ethyl α-hydroxymethylacrylate

The monomer reactivity ratios for copolymerization of 2-vinyl-4,4-dimethylazlactone (VA) and ethyl α-hydroxymethylacrylate (EHMA) were 0.20–0.24 and 0.53–0.74, respectively, which show that EHMA is slightly more reactive with VA than with itself and should lead to random copolymers favoring alternation. The VA–styrene (VA–St) system also has a tendency to form random copolymers but with increased tendency for alternation with both r₁ and r₂ between 0.18–0.22. T_g's of VA–EHMA and VA–St copolymers varied between 100 and 136°C, and 96 and 117°C, respectively. Thermolysis of VA–EHMA copolymers resulted in crosslinking via the ring-opening reaction of VA groups by EHMA alcohols, followed by transesterification involving EHMA units at higher temperatures leading to highly crosslinked structures. The performed dimer of EHMA and VA was also synthesized and found to be an effective crosslinking agent in free radical vinyl polymerizations.     

Chlorophosphonates: inexpensive precursors for stereodefined chloro-substituted olefins and unsymmetrical disubstituted acetylenes

New chlorophosphonates bearing a 1,3,2-dioxaphosphorinane ring which are useful for the stereospecific synthesis of 5-chlorofurfuryl substituted olefins and chloro-substituted dienes have been obtained by an easy, inexpensive route. The utility of some of these in the synthesis of ferrocenyl- and anthracenyl-substituted unsymmetrical acetylenes has been explored. The structures of the phosphonates (OCH(2)CMe(2)CH(2)O)P(O)CH(2)(C(4)H(2)ClO) (4) and (OCH(2)CMe(2)CH(2)O)P(O)(CH=CHCH(Cl)Ph (7) have been determined; in addition, the stereochemistry of (5-chlorofurfuryl)CH=CH(4-ClC(6)H(4)) (13b) and 2, 4-Cl(2)C(6)H(3)-CH=CH-CH=C(Ph)Cl (14a) is unambiguously proved by the X-ray structure determination.     

Hydrogen‐bonding and π–π inter­actions in 2‐amino‐4,6‐dimethyl­pyrimidinium salicylate

In the crystal structure of the title compound, C₆H₁₀N₃⁺·C₇H₅O₃⁻, the asymmetric unit contains four crystallographically independent 2‐amino‐4,6‐dimethyl­pyrimidinium and salicylate ions (Z = 8). In each of these, one of the pyrimidine N atoms is protonated, and the carboxyl­ate group of the salicylate ion inter­acts with the pyrimidine group through a pair of N—H⋯O hydrogen bonds, forming an R₂²(8) motif. The pyrimidine cations also form base pairs via a pair of N—H⋯N hydrogen bonds (involving the amino group and the unprotonated ring N atom), forming another R₂²(8) motif. Three such R₂²(8) motifs, fused together, constitute a closed cyclic aggregate, and the linking of these aggregates, arranged in consecutive layers, can be analysed in terms of off‐face stacking inter­actions.     

Stereoselective Synthesis of Polyfunctionalized Nitrothianes: Enhancement of Stereoselectivity by Microwaves

The Michael addition of nitromethane to (Z,Z)-2,2′-thiobis(1,3-diarylprop-2-en-1-ones) in the presence of NaOEt in dimethylformamide (DMF)/alcohol under thermal conditions affords a diastereomeric mixture of 2a,6e-diaroyl-3a,5e-diaryl-4e-nitrothianes and 2e,6e-diaroyl-3e,5e-diaryl-4e-nitrothianes with a dr of ～3:1/4:1 respectively. This reaction under microwave irradiation in DMF/alcohol afforded solely 2a,6e-diaroyl-3a,5e-diaryl-4e-nitrothianes, disclosing enhancement of stereoselectivity by microwaves.

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