Heterogeneous Catalytic Approaches in C-H Activation Reactions

This review summarizes the development of user-friendly, recyclable and easily separable heterogeneous catalysts for C–H activation during the last decade until December 2015

Efekti supstituenata na 13C-NMR hemijska pomeranja 3-metilen-4-supstituisanih-1,4-pentadiena - deo I

The principles of linear free energy relationships were applied to the 13C substituent chemical shifts (SCS) of the carbon atoms in the unsaturated chain of 3-methylene-4-substituted-1,4-pentadienes. Correlations of the SCS with the substituent parameters of Swain and Lupton provide a mutually consistent picture of the electronic effects in these compounds. The pattern of the electronic effects can be fully rationalized by a model based on the direct transmission of substituent effects through-space (direct through-space field effects), and via conjugative interactions (resonance effects), or by substituent-induced polarization of the ¶-system in the unsaturated chain (¶-polarization effect). Semi-empirical MNDO-PM3 calculations suggest the s-cis conformation of 3-methylene-4-substituted-1,4-pentadienes as the one with minimal heat of formation.Na 13C supstituentska hemijska pomeranja (SHP) ugljenikovih atoma u nezasićenom lancu 3-metilen-4-supstituisanih-1,4-pentadiena su primenjeni principi linearne korelacije slobodne energije. Korelacije SHP sa supstituentskim parametrima Swain-a i Lupton-a pružaju usaglašenu sliku elektronskih efekata u ovim jedinjenjima. Koncept elektronskih efekata može u potpunosti biti objašnjen modelom koji se zasniva na direktnom prenošenju efekata supstituenata kroz prostor (direktni efekti polja kroz prostor) i preko konjugacionih interakcija (rezonancioni efekti), ili putem supstituentom izazvane polarizacije ¶-sistema u nezasićenom lancu (efekti ¶-polarizacije). MNDO-PM3 semiempirijska izračunavanja upućuju na s-cis konformaciju 3-metilen-4-supstituisanih-1,4-pentadiena kao konformaciju sa minimalnom energijom obrazovanja

Linear free energy relationships of the H-1 and C-13 NMR chemical shifts of 3-methylene-2-substituted-1,4-pentadienes

Linear free energy relationships (LFER) were applied to the H-1 and C-13 NMR chemical shifts (delta(N), N=H-1 and C-13, respectively) in the unsaturated backbone of cross-conjugated trienes 3-methylene-2-substituted-1,4-pentadienes. The NMR data were correlated using five different LFER models, based on the mono, the dual and the triple substituent parameter (MSP, DSP and TSP, respectively) treatment. The simple and extended Hammett equations, and the three postulated unconventional LFER models obtained by adaptation of the later, were used. The geometry data, which are needed in Karplus-type and McConnell-type analysis, were obtained using semi-empirical MNDO-PM3 calculations. In correlating the data the TSP approach was more successful than the MSP and DSP approaches. The fact that the calculated molecular geometries allow accurate prediction of the NMR data confirms the validity of unconventional LFER models used. These results suggest the s-cis conformation of the cross-conjugated triene as the preferred one. Postulated unconventional DSP and TSP equations enable the assessment of electronic substituent effects in the presence of other interfering influences

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride

1-Cyclopropylcyclopropanecarboxylic acid (2), which is accessible on a large scale (900 mmol) from 1-bromo-1-cyclopropylcyclopropane (1) in 64% yield (89% on a 12.4 mmol scale), has been subjected to a Curtius degradation employing the Weinstock protocol to furnish the N-Boc-protected (1-cyclopropyl)cyclopropylamine 3 (76%). Deprotection of 3 with hydrogen chloride in diethyl ether gave the (1-cyclopropyl)cyclopropylamine hydrochloride (4·HCl) in 87% yield

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

Efficient and scalable syntheses of enantiomerically pure (2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-mono(di,tri)fluoromethylcyclopropyl]alanines 9a-c, as well as allo-D-threonine (4) and (2S,3R)-β-methylphenylalanine (3), using the Belokon' approach with (S)- and (R)-2-[(N-benzylprolyl)amino]benzophenone [(S)- and (R)-10] as reusable chiral auxiliaries have been developed. Three new fluoromethyl analogues of the naturally occurring octadepsipeptide hormaomycin (1) with (fluoromethylcyclopropyl)alanine moieties have been synthesized and subjected to preliminary tests of their antibiotic activity