Jaroslaw Romanski

Thioformaldehyde S‐sulfide (Thiosulfine)

Matrix isolation spectroscopy allows the direct identification of ylide 1 and its cyclic isomer 2. They were obtained by pyrolysis of 1,2,4-trithiolane under high vacuum; the cyclic compound forms from 1 by thermal ring closure in a kinetically controlled reaction.

Functional Group Transformations in Derivatives of 6-Oxoverdazyl

Transformations of functional groups, such as OCH2Ph, OCOPh, NO2 and I, in 1,3,5-triphenyl-6-oxoverdazyls 1a-1e were investigated in order to expand the range of synthetic tools for incorporation of the verdazyl system into more complex molecular architectures and to increase spin delocalization. Thus, Pd-catalyzed debenzylation of the OCH2Ph group or basic hydrolysis of the OCOPh group gave the phenol functionality, which was acylated, but could not be alkylated. Orthogonal deprotection of diphenol functionality was also demonstrated in radical 1c. Pt-catalyzed reduction of the NO2 group led to the aniline derivative, which was acylated. Attempted C-C coupling reactions to iodophenyl derivatives 1e and 5e were unsuccessful. Selected verdazyl radicals were characterized by EPR and electronic absorption spectroscopy, and results were analyzed with the aid of DFT computational methods.

Trifluoro­meth­yl derivatives of penta­cyclo­[5.4.0.02,6.03,10.05,9]undeca­ne

Three cage-like polycyclic compounds, viz. exo-8-(trifluoromethyl)pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecan-endo-8-ol, C12H13F3O, 5-(trifluoromethyl)-4-oxahexacyclo[5.4.1.0(2,6).0(3,10).0(5,9).0(8,11)]dodecan-3-ol, C12H11F3O2, and N-[exo-11-(trifluoromethyl)-endo-11-(trimethylsilyloxy)pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecan-8-ylidene]aniline methanol solvate, C21H24F3NOSi.CH4O, were obtained from the corresponding oxo derivatives by nucleophilic trifluoromethylation with (trifluoromethyl)trimethylsilane in 1,2-dimethoxyethane solution in the presence of CsF. The crystal structures show that the addition of trifluoromethanide occurs exclusively from the exo face of the polycyclic ketones. Further examination of the crystal structures, together with that of the starting pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione, C11H10O2, showed that increasing substitution at the 8- and/or 11-positions in the cage molecules increases the non-bonded intramolecular C...C distances at the mouth of the cage and changes the puckering of the five-membered rings involving the 8- and 11-positions from an envelope towards a distorted half-chair conformation. Intermolecular co-operative O-H...O hydrogen bonds in the endo-8-ol compound link the molecules into tetramers.

Gas-phase generation and matrix isolation of the methylsulfonyl radical CH₃SO₂˙ from allylmethylsulfone.

The atmospherically highly relevant methylsulfonyl radical (CH3SO2(•)) was generated by high-vacuum flash pyrolysis (HVFP) of allylmethylsulfone and isolated in an argon matrix at 10 K; the allyl radical formed as the cofragment. Upon thermolysis, the methylsulfonyl radical undergoes partial decomposition, leading to substantial amounts of sulfur dioxide in the matrix. The title compound was characterized through the assignment of eight fundamental IR bands of its CD3 and (13)CH3 isotopologues and the excellent agreement with the B3LYP/6-311+G(3df,3pd) computed harmonic vibrational frequencies. The two most intense absorptions were found at 1267.1 and 1067.6 cm(-1). In extension of this study S-methyl methanethiosulfonate was found to be another suitable, although less efficient, precursor for the gas-phase generation of the methylsulfonyl radical.

Matrix Isolation Studies on Sulfur Heterocycles and Related Species

Abstract The matrix isolation technique in combination with vacuum pyrolysis, photochemistry, and quantum mechanical computations was applied to study the structures and reactivities of dimethoxycarbene (DMC) and 1,3-dithian-2-ylidene. 1,2,4-Trithiolane was used for the generation of thioformaldehyde S-sulfide and the isomeric dithiirane. Irradiation of thioformaldehyde S-oxide in argon matrix at 10 K led to the first isolation of parent oxathiirane as well as HCSOH, a remarkable species with a rare formal carbon–sulfur triple bond.

Application of “Click” Cycloaddition for Synthesis of New Sulfur-Containing Oligomeric System

Abstract The efficient synthesis of new sulfur-containing macrocycles via “click”-type alkyne–azide cycloaddition was described. Preliminarily, under aqueous conditions (water–methanol) using CuSO4/sodium ascorbate as a source of Cu(I), the yields of the products were very poor. Using the Cu(I) in nonaqueous solution (MeCN), the yields of the products grow significantly (approx. 50%). GRAPHICAL ABSTRACT

Induction of Columnar Discotic Behavior in Verdazyl Radicals with Alkylsulfanyl Substituents

Abstract Substitution of the 1,3,5-triphenyl-6-oxoverdazyl radical with n-alkylsulfanyl groups lead to derivatives 1[n], which exhibit a columnar rectangular phase (Colr ) below 60 °C. Compounds 1[n] have a broad absorption band in the visible region with maxima at 540 and 610 nm and redox potentials E0/+1 1/2 = +0.99 V and E0/−1 1/2 = −0.45 V vs. SCE. Time-of-flight (TOF) investigation of 1[8] revealed hole mobility of μh = 1.52 × 10−3 cm2 V−1 s−1 in the columnar phase with an activation energy Ea = 0.06 ± 0.01 eV. Magnetization studies of 1[8] demonstrated nearly ideal paramagnetic behavior in both solid and fluid phases above 200 K and weak antiferromagnetic interactions at low temperatures. Verdazyl derivatives 1[n] were prepared in a sequence of reactions starting from 1-bromo-3,4,5-trifluorobenzene by alkylsulfanylation, followed by hydrazinylation, and finally 6-oxoverdazyl ring assembly using the Milcent method. GRAPHICAL ABSTRACT

Prototypical Triplet Alkyl Phosphonatocarbenes

The current case study focuses on the generation, identification, and characterization of two representative mono- and disubstituted alkyl phosphonatocarbenes by means of matrix isolation techniques in conjunction with density functional theory [B3LYP/6-311++G(d,p)] and coupled cluster [CCSD(T)/cc-pVXZ, X = D, T] computations. The EPR measurements identify both carbenes as triplet ground-state species with D values of 0.660 and 0.623 cm(-1), respectively, exhibiting persistency toward intramolecular reactions (the EPR signal observable in perfluoromethylcyclohexane up to around 70 K for the disubstituted molecule). While the reaction of the carbene center of the conformationally rich tetramethyl bisphosphonatocarbene with the CH bonds of the methyl groups leads to phosphaoxetane at room temperature, its fragmentation via a Wittig-type reaction during high vacuum flash pyrolysis (HVFP) results in dimethyl vinylphosphonate and methyl metaphosphate. The latter has been observed for the first time as an isolated entity.

UNEXPECTED PRODUCTS FROM THE REACTION OF 2,2,4,4-TETRAMETHYLCYCLOBUTANE-1,3-DIONE WITH THE MAKOSZA REAGENT

Reaction of 2,2,4,4-tetramethylcyclobutane-1,3-dione (2) under phase-transfer-catalysis (PTC) conditions (CHCl3/aqueous NaOH) yielded a complex mixture of unexpected products (Scheme 2). From the organic phase, three ring-enlarged products 7-9 with a cyclopentane-1,3-dione (cf. 7 and 9) or a cyclopentenone skeleton (cf. 8) were isolated in low yield. After acidification of the aqueous phase, the oily residue was treated with CH2N2 , and methyl 3-oxopentanoate 12 and dimethyl 2-hydroxybutanedioate 13 were obtained in almost equal amounts. The structures of 8 and 9 were established by X-ray crystal-structure analysis (Fig.). Mechanisms for the formation of the products, initiated by nucleophilic attack of trichloromethanide ion and opening of the cyclobutane ring, are proposed in Schemes 3 and 4.

Application of HPLC for the screening of separation of new macrocyclic systems

GRAPHICAL ABSTRACT ABSTRACT The efficient synthesis of new macrocyclic systems via nucleophilic ring opening reaction of epoxides by thiols was described. Initially new macrocyclic compounds were obtained as a mixture of diastereomers. Preparative thin layer chromatography was applied to separate meso and pairs of enantiomer. The identification of products using a chiral HPLC column and mass spectroscopy was utilized.