Showing papers on "Grignard reaction published in 1995"

High affinity and selectivity on 5-HT1A receptor of 1-aryl-4-[1-tetralin)alkyl]piperazines. 2.

Abstract: Several 4-alkyl-1-arylpiperazines that present a tetralin moiety on the terminal part of the side chain were synthesized in order to increase the selectivity on the 5-HT1A versus D-2, alpha 1, sigma, and other 5-HT receptors Many changes have been effected on previous structures of type 3(1-aryl-4-[3-(1,2-dihydronaphthalen-4-yl)-n-propyl]piperazines) Several synthetic procedures were followed to obtain the final products, depending on the presence or absence of a double bond, as well as of a heteroatom on the side chain In the first case versatile use of Grignard reaction was made, whereas in the second one usual synthetic ways were applied Final compounds were evaluated for in vitro activity on dopamine D-1 and D-2, serotonin 5-HT1A, 5-HT1B, 5-HT1C, and 5-HT2, alpha 1 adrenergic, and sigma receptors by radioreceptor binding assay For the 2-MeO-Ph, 2-pyridyl, and unsubstituted phenyl N-piperazine derivatives, low IC50 values (03 nM) on 5-HT1A receptors and high selectivity values were observed

Detection of intermediates in grignard reaction on the magnesium surface

Abstract: Benzyl radicals and ion-radical pairs (RHal - ....Mg + . n ) have been detected on a magnesium surface by electron spin resonance (ESR) spectroscopy during benzyl halide reactions with magnesium at low temperatures. The ratio of these intermediates depends on the carbon-halogen bond energy in the starting benzyl halide, the nature of the magnesium surface and the degree of magnesium aggregation. Polymagnesiumbenzyl chlorides were formed in small amounts and only monomagnesium organic compounds were formed from benzyl bromide and benzyl iodide

A method for synthesis of fluorine compounds using abnormal Grignard reaction of halothane. II: Reaction with aldehydes and unsaturated ketones

Abstract: In an abnormal Grignard reaction of halothane, the primary Grignard reagent reacts with another mole of halothane to give 1-bromo-1-chloro-2,2,2-trifluoroethylmagnesium bromide, which in turn reacts with a carbonyl compound to give 1-bromo-1-chloro-2,2,2-trifluoroethyl carbinols and their dehalogenation products, 1-chloro-2,2-difluoroethenyl carbinols. We examined the application of this method to aldehydes and to unsaturated ketones. Aldehydes were much less reactive than ketones, and needed higher reaction temperature. However, elevation of temperature caused dehalogenation of the primary products to 1-chloro-2,2-difluoroethenyl derivatives. These derivatives were treated with hydrogen fluoride to afford 1-chloro-1-(trifluoromethyl)ethene derivatives. The reaction of α,β-unsaturated ketones mainly gave 1,2-addition products of the Grignard reagent, while 3-methyl-2-cyclohexenone gave mainly the 1,4-adducts.

Terpenes and terpene derivatives, XXXIII. Synthesis of rac‐cis‐ and ‐trans‐dracunculifoliol and their 10‐epimers

Abstract: The cis-aldehyde 9, a key intermediate in the total synthesis of cis-dracunculifoliol (1) previously isolated from Vassoura oil, was prepared starting from the bicyclic enone 5 via the nitrile 8. Grignard reaction of 9 led exclusively to epi-1. Oxidation to the ketone 10 followed by reduction gave a separable mixture of the natural isomer 1 and epi-1. – The synthesis of trans-dracunculifoliol (2) starts with the 6-methoxytetralone 14. After some usual steps, the trans-octalin 17 was obtained. MMPP-HIO4 oxidation gave compound 19 which was transformed into the iodo ester 26, precursor of the hydrindane ester 27. Analogously to the synthesis of epi-1 the epi-trans-dracunculifoliol (epi-2) was formed via alcohol 28 and aldehyde 29. Oxidation ( 30) and reduction furnished the natural trans alcohol 2. – Olfactory evaluation of the purified isomers 1, epi-1, 2, and epi-2 showed that all of them possess only a weak, woody odor. Therefore, the dracunculifoliols 1 and 2 are not responsible for the typical earthy, leathery, and spicy odor of the Vassoura oil.

Synthesis of Spiro[cyclohexane-1,2′-[2H]indene] derivatives as inhibitors of steroid 5α-reductase

Abstract: The spiro[cyclohexane-1,2′-[2H]indene] derivatives 15a,b with molecular dimensions and nucleophilic functional groups similar to known steroid 5α-reductase inhibitors (e.g.2) were synthesized. The spiro[cyclohexane-1,2′-[2H]indene]-1′(3′H),4-dione (5) was synthesized from 5-methoxyindan-l-one ( = 2,3-dihydro-5-methoxy-1H-inden-1-one). A Grignard reaction and a dehydration step led to the cyclohexene (±)-7 which, upon a stereoselective hydrogenation catalyzed by Raney-Ni under mild conditions, gave 8a as a pure epimer. Further hydrogenation and hydrogenolysis of 8a over Pd/C at room temperature reduced the keto group to give pure 9a. Finally, the 5′-substituted derivatives 12a, 14a, and 15a were generated by deprotection and Heck-type reaction.

Optical Properties of Poly(pentafluorophenylsilyne) Prepared by Electrochemical Polymerization

Abstract: The first polysilyne having a perfluorinated aryl group, poly(pentafluorophenylsilyne), was prepared through a combination of the Grignard reaction of bromopentafluorobenzene and tetrachlorosilane and the subsequent electrochemical polymerization using a magnesium electrode. The absorption and emission spectra of the polymer showed the characteristic of polysilyne which has a silicon network structure. The emission decay of poly (pentafluorophenylsilyne) measured by the time-resolved single photon counting technique showed non-single exponential kinetics. These optical properties were compared with those of poly(phenylsilyne).

4-(2,2,2-trifuluoroethoxy)-3,5-difluorobenzene derivetive

Abstract: PURPOSE:To obtain a new liquid crystal compound usable as an additive capable of lowering the threshold voltage of a liquid crystal composition and increasing the upper limit temperature of the liquid crystal phase of the composition. CONSTITUTION:A 4-(2,2,2-trifluoroethoxy)-3,5-difluorobenzene derivative of formula I (R is a 1-10C straight-chain alkyl or straight-chain alkenyl; L and M are single bound or CH2CH2; at least one of L and M is single bond), e.g. 1-[trans-4-(trans-4-propylcyclohexyl) cyclohexyl]-3,5-difluoro 4-(2,2,2- trifluoroethoxy) benzene. The compound of formula I wherein L and M are single bond and R is a 1-5C alkyl (R ) (the compound of formula Ia) can be produced by reacting a compound of formula IV with magnesium to obtain a Grignard reaction agent, reacting the agent with a compound of formula V, subjecting the reactional product to dehydration and hydrogenation to obtain a mixture of isomers having different steric configurations of the central cyclohexane ring and resolving the isomer mixture or isomerizing with a base.

Preparation of Organomagnesium Compounds

Abstract: This chapter discusses the preparation of organomagnesium compounds. The most common method for preparing organomagnesium compounds remains the classical Grignard reaction of magnesium with organic halides. The majority of solutions that are commercially available are prepared in this way. Several manufacturers have facilities for preparing Grignard reagents on a “fine chemicals” scale, and a surprising number are offered for sale as laboratory chemicals. A variety of methods for preparing organomagnesium compounds utilize elemental magnesium, and for many of them the purity and form of the metal is important or even critical. Magnesium is readily available in a purity of 99.8%, and this grade is satisfactory for many routine purposes. Sublimed magnesium is also commercially available, typically with less than 10 ppm impurities; magnesium containing only zinc at over 1 ppm has been obtained by this method. Sublimed magnesium is usually supplied in the form of chips, but often has a large effective surface area. The mechanism of the reaction between organic halides and magnesium, leading to organomagnesium compounds, has been the subject of much speculation and study.

Synthesis of Spiro(cyclohexane‐1,2′‐(2H)indene) Derivatives as Inhibitors of Steroid 5α‐Reductase.

Abstract: The spiro[cyclohexane-1,2′-[2H]indene] derivatives 15a,b with molecular dimensions and nucleophilic functional groups similar to known steroid 5α-reductase inhibitors (e.g.2) were synthesized. The spiro[cyclohexane-1,2′-[2H]indene]-1′(3′H),4-dione (5) was synthesized from 5-methoxyindan-l-one ( = 2,3-dihydro-5-methoxy-1H-inden-1-one). A Grignard reaction and a dehydration step led to the cyclohexene (±)-7 which, upon a stereoselective hydrogenation catalyzed by Raney-Ni under mild conditions, gave 8a as a pure epimer. Further hydrogenation and hydrogenolysis of 8a over Pd/C at room temperature reduced the keto group to give pure 9a. Finally, the 5′-substituted derivatives 12a, 14a, and 15a were generated by deprotection and Heck-type reaction.

Synthetic Studies Towards Faveline Methyl Ether.

Abstract: A convergent approach to faveline methyl ether based on Claisen rearrangement is delineated. Thus the benzylic and allylic alcohol substrate was assembled by a Grignard reaction, and the rearrangement product was oxidized and cyclized. Double bond isomers of faveline methyl ether were obtained.

Synthesis of Azasugars by Grignard Reaction on Glycosylamines.

Abstract: Pyrrolidines 5a-b, and piperidines 10a,b and 15, were synthesised by Grignard reaction on a glycosylamine, easily obtained from the parent sugar and a primary amine, followed by cyclization with triflic anhydride.

A Convenient Approach to Perfluorinated Organosilicons. Preparation of a Fluorinated Polysiloxane Precursor.

Abstract: Addition of perfluorooctyl iodide to the double bonds of vinyltrimethylsilane and 1,3-divinyltetramethyldisiloxane, followed by a reduction of the carbon-iodide bond, gives the corresponding C 8 F 17 CH 2 CH 2 Si moicty. Following this approach, |C 8 F 17 CH 2 CH 2 Si(Me)O| 4 . a precursor of highly fluorinated silicones. was conveniently prepared. without using hydrosilylation or Grignard reaction.

Chemoselective Preparation of Ketones by the Grignard Reaction of N- Acylpyrazoles.

Abstract: N-Acylpyrazoles afford chemoselectively the corresponding ketones in good yields by the use of equimolar amounts of Grignard reagent. In the case of an optically active N-acylpyrazole, optical asymmetry was retained in comparable optical yield. Ketone formation by the Grignard reactions can be regarded as an important functionalization in a synthetic loop using pyrazoles as the auxiliary compound.