Synthesis of Unexpected Dimethyl 2-(4-Chlorophenyl)-2,3-dihydropyrrolo[2,1-a]isoquinoline-1,3-dicarboxylate via Hydrolysis/Cycloaddition/Elimination Cascades: Single Crystal X-ray and Chemical Structure Insights

Hydrolysis/[3 + 2] cycloaddition/elimination cascades employed for the synthesis of unexpected tricyclic compound derived from isoquinoline. Reaction of ethylene derivative 1 with the isoquinoline ester iminium ion 2 in alkaline medium (MeOH/NEt3) under reflux for 1 h resulted in the formation of the fused pyrrolo[2,1-a]isoquinoline derivative 3. Its structure was elucidated by X-ray single crystal and other spectrophotometric tools. Hirshfeld calculations for 3 and its crystal structure analysis revealed the importance of the short O…H (19.1%) contacts and the relatively long H…C (17.1%), Cl…H (10.6%) and C…C (6.1%) interactions in the molecular packing. DFT calculations were used to compute the electronic and spectroscopic properties of the studied system. The studied compound has polar nature (3.5953 Debye). TD-DFT calculations assigned the shortest wavelength band (220 nm) to the HOMO−1→LUMO+2 (57%), HOMO−1→LUMO+4 (14%) mixed excitations. The calculated NMR chemical shifts correlated very well with the experimental data (R2 = 0.93–0.94).

[3+2] Cycloaddition Reaction for the Stereoselective Synthesis of a New Spirooxindole Compound Grafted Imidazo[2,1-b]thiazole Scaffold: Crystal Structure and Computational Study

A new spirooxindole hybrid engrafted imidazo[2,1-b]thiazole core structure was designed and achieved via [3+2] cycloaddition reaction approach. One multi-component reaction between the ethylene derivative based imidazo[2,1-b]thiazole scaffold with 6-Cl-isatin and the secondary amine under heat conditions afforded the desired compound in a stereoselective manner. The relative absolute configuration was assigned based on single-crystal X-ray diffraction analysis. Hirshfeld calculations for 4 revealed the importance of the H…H (36.8%), H…C (22.9%), Cl…H (10.4%) and S…H (6.6%), as well as the O…H (4.7%), N…H (5.3%), Cl…C (1.6%), Cl…O (1.0%) and N…O (0.5%) contacts in the crystal stability. DFT calculations showed excellent straight-line correlations (R2 = 0.9776–0.9962) between the calculated and experimental geometric parameters. The compound has polar nature (3.1664 Debye). TD-DFT and GIAO calculations were used to assign and correlate the experimental UV-Vis and NMR spectra, respectively.

Theoretical Studies on the Reactions of Aryl and Hetaryl Thioketones with Nitrilimines

<p>Many synthetic routes to constructing biologically-active heterocyclic compounds are made feasible through the (3 + 2) cycloaddition 32CA reactions. Due to a large number of possible combinations of several heteroatoms from either the three-atom components (TACs) or the ethylene derivatives, the potential of the 32CA reactions in heterocyclic syntheses is versatile. Herein, the 32CA of thiophene-2-carbothialdehyde derivatives and <i>C</i>,<i>N</i>-disubstituted nitrilimines have been studied through density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) level of theory. In the present study, one-step (3 + 2) and two-step (4 + 3) mechanisms of the addition of the TAC and ethylene derivative have been investigated. In all reactions considered, the one-step (3 + 2) cycloaddition is preferred over the two-step (4 + 3) cycloaddition. The TAC chemoselectively adds across the thiocarbonyl group present in the ethylene derivative in a (3 + 2) fashion to form the corresponding cycloadduct. Analysis of the electrophilic ( and nucleophilic ( Parr functions at the various reaction centers in the ethylene derivative show that the TAC adds across the atomic centers with the largest Mulliken atomic spin densities, which is in total agreement with the experimental observation. The selectivities observed in the title reaction are kinetically controlled.</p>

Theoretical Studies on the Reactions of Aryl and Hetaryl Thioketones with Nitrilimines

<p>Many synthetic routes to constructing biologically-active heterocyclic compounds are made feasible through the (3 + 2) cycloaddition 32CA reactions. Due to a large number of possible combinations of several heteroatoms from either the three-atom components (TACs) or the ethylene derivatives, the potential of the 32CA reactions in heterocyclic syntheses is versatile. Herein, the 32CA of thiophene-2-carbothialdehyde derivatives and <i>C</i>,<i>N</i>-disubstituted nitrilimines have been studied through density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) level of theory. In the present study, one-step (3 + 2) and two-step (4 + 3) mechanisms of the addition of the TAC and ethylene derivative have been investigated. In all reactions considered, the one-step (3 + 2) cycloaddition is preferred over the two-step (4 + 3) cycloaddition. The TAC chemoselectively adds across the thiocarbonyl group present in the ethylene derivative in a (3 + 2) fashion to form the corresponding cycloadduct. Analysis of the electrophilic ( and nucleophilic ( Parr functions at the various reaction centers in the ethylene derivative show that the TAC adds across the atomic centers with the largest Mulliken atomic spin densities, which is in total agreement with the experimental observation. The selectivities observed in the title reaction are kinetically controlled.</p>

Die Darstellung sterisch anspruchsvoller Phosphinoester und ihre Verwendung zur Synthese von Rhodium(I)-und Rhodium(III)-Komplexen [1] / The Preparation of Sterically Demanding Phosphinoesters and their Use for the Synthesis of Rhodium(I) and Rhodium (III) Complexes

Two routes for the preparation of sterically demanding phosphinoesters RR′P(CH2)nCO2Me (n=1,2 or 3) and RR′P(CH2)nCO2Et (n=1 or 2) have been developed: (1) reaction of trimethyl-silyl phosphines RR′PSiMe3 (R=R′=/Pr. rBu) with ω-chloroalkylesters, and (2) hydrophos- phination of secondary phosphines HP(R)Ph (R = Me, Et. Pr. iPr, iBu) with unsaturated carboxylic esters. From iPr2PCH2CO2Me (3) and iPr2PCH2CO2Et (4), a variety of rhodium(I) and rhodium(III) complexes, mainly with alkyne and vinylidene ligands, have been prepared. Compound [RhCl(C8H14)2]2 (19) reacts with four equiv. of 3 to give [RhCl(iPr2PCH2CO2Me)2] (20) which on further treatment with CO affords the carbonyl complex trans-[RhCl(CO)(iPr′>PCH2CO2Me)2] (21). The related ethylene derivative trans-[RhCl(C2H4)(iPr2PCH2CO2Me)2] (23) is obtained from [RhCl(C2H4)2]2 (22) and 3. Compound 20 reacts with H2 and HCl by oxidative addition to yield [RhHXCl(iPr2PCH2CO2Me)2] (24, 25) and with RC≡CR′ to give the alkyne complexes trans-[RhCl(RC≡CR′)(iPr2PCH2CO2Me)2] (26-28). The analogous compounds trans- RhCl(HC≡CR)(iPr2PCH2CO2Me)2] (29, 30), equally prepared from 20 and HC≡CR, both rearrange thermally and photochemically to produce the vinylidene isomers trans-[RhCl(=C=CHR)(iPr2PCH2CO2Me)2] (31, 32). In contrast, propyne reacts with 20 to give the allene complex trans-[RhCl(CH2=C=CH2)(iPr2PCH2CO2Me)2] (33). The synthesis of [RhCl(iPr2PCH2CO2Et)2] (34) and the corresponding alkyne and vinylidene adducts 35 and 36, obtained with HC≡CCO2Me as the substrate, is also described.