Functionalization of <Emphasis Type="Italic">N-tert</Emphasis>-butoxycarbonyl-7-and <Emphasis Type="Italic">N-tert</Emphasis>-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes. A route to a ferruginine homolog

N-tert-Butoxycarbonyl-7-and N-tert-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes are convenient substrates for further modification using replacement of the Br atom by a cyano group or a Li atom. Treatment of lithium derivatives with dimethylformamide and N-methoxy-N-methylacetamide gave the corresponding α,β-unsaturated aldehydes (67–84%) and ketones (∼70%). Ketone 4b is a direct precursor of a homolog of the alkaloid ferruginine. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1794–1796, September, 2007.     

Carbonylation of Difluoroalkyl Bromides Catalyzed by Palladium

Although important progress has been made in the fluoroalkylation reactions, the transition‐metal‐catalyzed carbonylative fluoroalkylation reaction remains challenging so far. Herein, we report the first example of a Pd‐catalyzed carbonylation of difluoroalkyl bromides with (hetero)arylboronic acids under one atmosphere pressure of CO. The reaction can also be extended to the aryl potassium trifluoroborate salts. The advantages of this protocol are synthetic simplicity, broad substrate scope, and excellent functional group compatibility. The resulting difluoroalkyl ketones can serve as versatile building blocks for the synthesis of various useful fluorinated compounds.     

Terminal‐Selective Functionalization of Alkyl Chains by Regioconvergent Cross‐Coupling

Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C?H bond functionalization methods. We describe herein a new step‐economical approach that enables C?C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross‐coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross‐coupling then provided access to the corresponding linear arylation product in only two steps.     

Hydrophobic hydration of some different types of quaternary ammonium bromides in mixtures of water andN,N-dimethylformamide

Enthalpies of solution of methyltributylammonium bromide, tetraethanolammonium bromide, and three azoniaspiroalkane bromides in binary solvent mixtures of water and N,N-dimethylformamide have been measured calorimetrically at 298.15^oK over the whole mole fraction range. The results are interpreted in terms of a simple hydration model with two parameters and compared with those of the corresponding tetraalkylammonium bromides. Enthalpic studies with different types of quaternary ammonium bromides are useful in reexamining the assumptions and limitations of the hydration model.     

Phenacyl bromide: A versatile organic intermediate for the synthesis of heterocyclic compounds

Phenacyl bromides are used as a building blocks in synthetic organic chemistry, which serves as a key model for the development of various biologically important heterocyclic compounds and other industrially important scaffolds. This review covers recent synthetic advances in the preparation of heterocyclic compounds utilizing various phenacyl bromides. A wide range of five- and six-membered heterocyclic compounds as well as fused heterocyclic compounds were synthesized efficiently from the phenacyl bromide precursors through one-pot multicomponent reactions.     

Helical chirality of 1-phenacyl-1,10-phenanthrolinium bromides

Evidence for non-coplanarity of the pyridine and pyridinium rings in a series of 1-phenacyl-1,10-phenanthrolinium bromides was gleaned from ¹H-NMR data recorded in DMSO-d ₆ solution. The X-ray structure of 1-(4-chlorophenacyl)-1,10-phenanthrolinium bromide, as representative of this series, was determined in order to establish whether such a molecular distortion occurs in the solid state. The title compound crystallizes in the space group C2/c as a sesquihydrate of formula C₂₀H₁₄BrClN₂O·1.5H₂O with a = 35.7348(3) Å, b = 5.3468(1) Å, c = 21.7312(2) Å, = 116.4076(4)° and Z = 8. In the crystal, the helical chirality is manifested as a pronounced twist in the phenanthrolinium moiety, with the pyridine and pyridinium rings inclined at 6.8(2)°. This distortion is attributed to intramolecular hydrogen bonding of type C–H···N involving the methylene group and the uncharged nitrogen atom of the phenanthrolinium moiety. In the crystal, the cations surround an intricate array of water molecules and bromide ions held together by O–H···Br^– hydrogen bonds and comprising infinite chains ···Br^–···H–O–H···Br^–···, cross-linked by water molecules.     

稀土溴化物与甘氨酸配合物标准摩尔生成焓的测定

采用量热法在２９８１５±０１０Ｋ测量了ＲＥＢｒ３·３Ｇｌｙ·３Ｈ２Ｏ（ＲＥ＝Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｙ；Ｇｌｙ为甘氨酸）和甘氨酸在水中的积分溶解热，及ＲＥＢｒ３·ｎＨ２Ｏ（ＲＥ＝Ｌａ、Ｃｅ、Ｐｒ时，ｎ＝７；ＲＥ＝Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｙ时，ｎ＝６）在甘氨酸水溶液中的积分溶解热。用本研究设计的热化学循环求得上述１０种ＲＥＢｒ３·３Ｇｌｙ·３Ｈ２Ｏ配合物的标准摩尔生成焓，并计算出它们的晶格能。     

2-HALOVINYL ARYL SULFONES: NEW COUPLING REAGENTS FOR CARBOXAMIDE FORMATION1

Abstract

E-2-Chlorovinyl p-nitrophenyl sulfone 6 and 2-bromo-2-trifluoromethylvinyl phenyl sulfone 7a reacted with carboxylic acids in the presence of a molar equiv of Et₃N affording the corresponding 2-acyloxyvinyl sulfones 8, 11, 17, 18, 22, 25, 28 and 29. The latter, on treatment with amines, gave amides 9, 13, 19, 23 and 26 and peptides 30 and 32. These reagents 6 and 7a were also used for the formation of N-methylanilides 13d, 13e, 19d, 23 and 26. Particularly, 6 was successfully used for synthesis of a macrocyclic lactam 23 involving a N-methylanilide moiety. The amidation reactions proceeded under essentially neutral conditions. Therefore, base-sensitive β-hydroxycarboxy-N-methylanilides such as 26, whose structural unit was involved in maytansine 5, could be prepared by the present method. The reagent 6 was also effective for the preparation of peptides such as Val-N-MeVal derivatives (e.g. 32), which were difficult to prepare by other methods.     

Electrical conductivity of the molten EuBr2–MBr binary mixtures (M = Li, Na, K, Rb, or Cs)

The electrical conductivity of all EuBr₂–alkali metal bromide liquid mixtures was measured as function of temperature over the whole composition range. The activation energy, E_A, was evaluated for all liquid mixtures. It was revealed that the classical Arrhenius dependence did not stand for any individual mixture. The obtained results were discussed in terms of complex formation in the melts.