Regiospecific photohydroxyalkylation of pentafluoropyridine

Irradiation of 1-hydroxyalkane solutions of pentafluoropyridine in the presence of benzo-phenone resulted in regiospecific substitution at position 4, thus forming 2,3,5,6-tetrafluoro-4-(1-hydroxyalkyl)pyridine.     

Isotope effects in the temperature dependence of the pure quadrupole resonance spectra of Cl35 and Cl37 in trichloracetic acid

Elastic and thermoeleastic constants, abrasive hardness and indentation hardness were measured on AgClO₃, NaClO₃ and NaBrO₃. The differences in the elastic behaviour of AgClO₃ and NaClO₃ correspond to those of AgCl and NaCl. They agree with similar effects in isotypic crystal groups if main group elements are replaced by subgroup elements. The mechanical properties of these three crystals are in a close relationship to those of NaCl.     

Alpha-substituted organic peroxides: synthetic strategies for a biologically important class of gem-dihydroperoxide and perketal derivatives

In this paper we review the recent developments in the synthesis of alpha-substituted hydroperoxides. Alpha-substituted hydroperoxides are interesting compounds due to their chemistry and bioactivity and as intermediates for the synthesis of other peroxides, of which cyclic peroxides are of major importance. Although the emphasis of this report will be on the derivatives of gem-dihydroperoxides, perketals, as well as the less studied nitrogen and sulfur derivatives, will also be covered.     

The role of multifunctionalized amine structure and reaction conditions on the transformations of crosslinked copoly(styrene-p-nitrophenylacrylate)

Crosslinked copoly(styrene-p-nitrophenylacrylates), containing 2% (1) or 4% DVB (2) were converted with various diaminoalkanes (1,2-diaminoethane 3a, 1,4-diaminobutane 3b, 1,8-diaminooctane 3c) to amides. The degree of additional crosslinking depended on the chain length of the diaminoalkane, the molar ratio of ester function in 1 or 2 to diaminoalkane, solvent polarity (dimethylformamide, chloroform, toluene), while reaction temperature (50 or 100°C) had only a minor effect. 2 was also converted with various amines bearing additional functional groups (ethanolamine, 3-amino-1-propanol, 4-aminomethylpyridine, 2-(2-aminoethylamino)-ethanol, 2-(2-aminoethoxy)-ethanol, 6-aminocaproic acid, N-propylaminomorpholine, 3-N,N-diethylamino-1-propylamine) to the corresponding amides. The swelling ability of the resins depended on the crosslinking of the starting copoly(styrene-p-nitrophenylacrylate) (1, 2), the structure of the amide, the degree of additional crosslinking, and solvent polarity (chloroform, dimethylformamide, methanol, toluene). The accessibility of nitrogen atoms in the polymer matrix was examined by EtX functionalization of the 3-N,N-diethylamino-1-propylamine derivative (10) and 4-aminomethylpyridine derivative (13), and more than 85% functionalization was found. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1699–1706, 1998     

Bromination of aromatic molecules with polymer supported reagents

Crosslinked co-poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes or respectively, and their reactivity studied in reactions with various aromatic molecules. Reagent was found in all cases to be milder than reagent and regiospecifically transformed alkoxy and amino substituted benzenes ( ) into 4-bromo derivatives, while corresponding reactions with resulted in dibromo derivatives. Several benzoheterocyclic molecules were converted with to substitution or addition products, i.e. 2,3-dibromo-N-methylpyrrole, 3-bromobenzo/b/thiophene, and 2,3-dibromo-2,3-dihydrobenzofuran. In the series of ortho-alkyl disubstituted benzene derivatives, i.e. o-xylene, indane, and tetraline, where the Mills-Nixon effect was established with various electrophilic reagents, bromination reactions with showed higher β-selectivity than the corresponding reactions with bromine. The rate of bromination in various alkyl substituted benzenes with reagent depended on the magnitude of the alkyl group, as well as the para/ortho regioselectivity, amounting to 100% in the case of tert-butylbenzene.     

Reductive ring cleavage of 1-alkyl-4-benzoylamino-5-phenyl-3-pyrazolidinones with raney-nickel alloy. Synthesis of N-benzoyl-3-alkylamino-3-phenylalanine amides from rel-(4R,5R)-4-benzoylamino-5-phenyl-3-pyrazolidinone

rel-(4R,5R)-4-Benzoylamino-5-phenyl-3-pyrazolidinone ( 1 ) was alkylated at position 1 with carbonyl compounds 2a-g . The corresponding rel-(4R,5R)-4-benzoylamino-5-phenyl-3-pyrazolidinone-1-azomethine imines 3a-g , were treated with sodium borohydride to give rel-(4R,5R)-1-alkyl-4-benzoylamino-5-phenyl-3-pyrazolidinones 4a-g . Reduction of pyrazolidinones 4a-g with Raney-nickel alloy in methanolic potassium hydroxide furnished rel-(4R,5R)-N-benzoyl-3-alkylamino-3-phenylalanine amides 5a-f .     

Study of incidence of DiPAMP ligand modification on the rhodium(I)-catalyzed asymmetric hydrogenation of α-acetamidostyrene

A series of P-stereogenic enantiopure 1,2-bis[(aryl)(phenyl)phosphino]ethane ligands was prepared through an extensive systematic incorporation of various substituents onto the P-o-anisyl rings of Knowles’ DiPAMP (DiPAMP = 1,2-bis[(o-anisyl)(phenyl)phosphino]ethane). The study of incidence of such modification on the Rh(I)-catalyzed hydrogenation of α-acetamidostyrene is reported revealing that substitution on position 3 is detrimental, while it is beneficial on position 5. Namely, a 2.5-fold increased catalyst activity coupled with a higher enantioselectivity (90% ee) was attained with the P-(2-MeO-3-naphthyl)-substituted ligand under mild conditions (1 bar H₂, rt in MeOH).