A rapid, mild procedure for the preparation of alkyl chlorides and bromides

1968 ◽  
Vol 46 (1) ◽  
pp. 86-87 ◽  
Author(s):  
J. Hooz ◽  
S. S. H. Gilani
Keyword(s):  
Carbon Tetrachloride ◽  
High Yield ◽  
Carbon Tetrabromide ◽  
Alkyl Bromides ◽  
Reaction Proceeds

Primary and secondary alkyl chlorides have been conveniently prepared by the reaction of tri-n-octylphosphine with carbon tetrachloride solutions of the corresponding alcohols. This rapid, high yield reaction proceeds with inversion of configuration. By using carbon tetrabromide the method has been extended to the synthesis of alkyl bromides.

Phosphonium salts. III. The action of cyanide ion and other nucleophiles on some bis-phosphonium salts

1969 ◽  
Vol 22 (7) ◽  
pp. 1405 ◽  
Author(s):  
JJ Brophy ◽  
MJ Gallagher
Keyword(s):  
Sodium Azide ◽  
Sodium Methoxide ◽  
Sodium Acetate ◽  
Potassium Cyanide ◽  
Dimethyl Sulphoxide ◽  
High Yield ◽  
Phosphonium Salts ◽  
Elimination Reaction ◽  
Cyanide Ion ◽  
Reaction Proceeds

Cyclic and acyclic bis-phosphonium salts with a two-carbon bridge are smoothly cleaved to phosphines in high yield by potassium cyanide in dimethyl sulphoxide. Evidence is presented that the reaction proceeds by an elimination-addition sequence. An elimination reaction also occurs when sodium methoxide, sodium azide, sodium acetate, and triethylamine react with ethane-1,2-bis(tri-phenylphosphonium) dibromide. ��� In a novel reaction, triphenylphosphine is converted into its oxide by a mixture of sodium azide and dimethyl sulphoxide.

Highly Diastereoselective and Irreversible Aldol Reactions of N-Sulfonylimidates

Synthesis ◽  
2016 ◽  
Vol 48 (19) ◽  
pp. 3413-3419 ◽  
Author(s):  
Hannah Bartrum ◽  
Sébastien Carret ◽  
Jean-François Poisson
Keyword(s):  
Lewis Acid ◽  
High Yield ◽  
Aldol Reactions ◽  
Titanium Complex ◽  
Reaction Proceeds

A mild method for the aldolization of N-sulfonylimidates was developed. The reaction proceeds in excellent diastereoselectivity to provide a range of useful β-hydroxyimidates in high yield. The innate reversibility of the reaction is suppressed by the use of a titanium complex as a Lewis acid.

4,5-Seco-4,6-cyclosteroids. III. Observations on the course of reductive rearrangement of 6β-Bromo-4β,5-epoxy-5β-cholestan-3β-ol

1969 ◽  
Vol 22 (4) ◽  
pp. 807 ◽  
Author(s):  
DJ Collins ◽  
JJ Hobbs ◽  
RJ Rawson
Keyword(s):  
Hydrogen Bromide ◽  
High Yield ◽  
Lithium Aluminium Hydride ◽  
Experimental Conditions ◽  
Lithium Aluminium ◽  
Reaction Proceeds ◽  
Derivatives Of

It has been shown that reductive rearrangement of 6β-bromo-4β,5-epoxy- 5β-cholestan-3β-ol (I) to 4,5-seco-4,6-cycle-6β-cholestane-3β,5α-diol (IXa) with lithium aluminium hydride in tetrahydrofuran proceeds via 6β-bromo-5β-cholestane-3β,5-diol (IIa). Relevant reactions of the latter and the corresponding 3-ketone are discussed. ��� Similar conversion of the 3-epimer of (I) into 4,5-seco-4,6-cyclo- 6β-cholestane-3α,5α-diol (XIIIa) in high yield indicates that reductive rearrangement of the 6β-bromo-5β-hydroxy moiety proceeds without participation of the 3-aluminate complex. Some derivatives of (XIIIa) are described. ��� Experimental conditions required for the conversion of (I) into (IXa) are defined. ��� Combined evidence indicates that the reaction proceeds in a concerted manner by essentially base-catalysed, 1,3-elimination of hydrogen bromide from diol (IIa) with 4,5-bond migration to give the formal intermediate 3β-hydroxy-4,5-seco-4,6-cyclo-6β-cholestan-5-one (VI), further reduced to (IXa).

scholarly journals Palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides

2017 ◽  
Vol 13 ◽  
pp. 2610-2616 ◽  
Author(s):  
Tao Fan ◽  
Wei-Dong Meng ◽  
Xingang Zhang
Keyword(s):  
Alkyl Radical ◽  
Functional Group ◽  
High Efficiency ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Type Reaction ◽  
Alkyl Bromides ◽  
Reaction Proceeds ◽  
Palladium Catalyzed ◽  
Hydroxy Groups

An efficient palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides has been developed. The reaction proceeds under mild reaction conditions with high efficiency and excellent functional group tolerance, even towards formyl and hydroxy groups. Preliminary mechanistic studies reveal that a secondary trifluoromethylated alkyl radical is involved in the reaction.

scholarly journals Copper(I)-Catalyzed Boryl Substitution of Allyl Aminals: Selective Synthesis of Linear γ-Aminoallylboronates

Synthesis ◽  
2017 ◽  
Vol 49 (21) ◽  
pp. 4738-4744 ◽  
Author(s):  
Hajime Ito ◽  
Yuta Takenouchi
Keyword(s):  
Amino Alcohol ◽  
High Yield ◽  
Selective Synthesis ◽  
Novel Approach ◽  
Reaction Proceeds ◽  
High Stereoselectivity

A novel approach for the selective synthesis of α-substituted γ-aminoallylboronates through a copper(I)-catalyzed γ-boryl-substitution of allyl aminals is developed. The reaction proceeds with high yield (up to 88%) and good E/Z selectivity (up to >95:5). Subsequent aldehyde allylation using allylboronates affords (Z)-anti-1,2-amino alcohol derivatives with high stereoselectivity (up to 91% yield, and up to 17:83 E/Z).

Enolic Ortho Esters. I. Preparation and Birch Reduction of Some Coumarinoid Ortho Esters

1989 ◽  
Vol 42 (8) ◽  
pp. 1235 ◽  
Author(s):  
DJ Collins ◽  
LM Downes ◽  
AG Jhingran ◽  
SB Rutschmann ◽  
GJ Sharp
Keyword(s):  
Carbon Tetrachloride ◽  
Acid Hydrolysis ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
High Yield ◽  
Ortho Ester ◽  
Birch Reduction ◽  
High Yields ◽  
Ortho Esters ◽  
Hydrolysis Of

Phenolic ortho esters such as 4′,4′-dimethylspiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (7b) and 4′,4′-dimethyl-3,4-dihydrospiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (9c) were prepared in low yields by reaction of 2H-1-benzopyran-2-one (5) or 3,4-dihydro-2H-1-benzopyran-2-one (8a) with 2,2-dimethyloxiran in carbon tetrachloride in the presence of boron trifluoride etherate. 3,4-Dihydrospiro[2H-1-benzopyran-2,2′-[1,3] dioxoan ] (9a) and the corresponding 7-methoxy compound (9e) were obtained in high yield by reaction of (8a) or its 7-methoxy analogue (8b) with 1,2-bis(trimethylsily1oxy)ethane (10) in the presence of trimethylsilyl trifluoromethane-sulfonate . Birch reduction of phenolic ortho esters such as (9c) and (9e) afforded the enolic ortho esters 4′,4′-dimethyl-3,4,5,8-tetrahydrospiro[2H-1-benzopyran-2,2′-[1,3] dioxola n] (11a) and 7-methoxy-3,4,5,8-tetrahydrospiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (llc) in high yields. Birch reduction of 4′,4′,5′,5′-tetramethylspiro[2H-1-benzopyran-2,2′-[1,3]dioxolan] (7c) gave a 1 : 3 mixture of 4′,4′,5′,5′-tetramethyl-3,4-dihydrospiro[2H-1-benzopyran-2,2′-[l,3] dioxolan ] (9d) and the corresponding 3,4,5,8-tetrahydro compound (11b). Acid hydrolysis of the enolic ortho ester (11a) gave 67% of 2-hydroxy-2-methylpropyl 3-(2-oxocyclohex-3-enyl) propanoate (20).

Selective transformations of secologanin: dihydroxylation

1981 ◽  
Vol 59 (2) ◽  
pp. 210-214 ◽  
Author(s):  
John Richard Purdy ◽  
Raymond G. Hamilton ◽  
Lalarukh Akhter ◽  
Stewart McLean
Keyword(s):  
High Yield ◽  
Side Chain ◽  
Conformational Preference ◽  
Large Excess ◽  
Reaction Proceeds ◽  
Small Excess

Sweroside tetraacetate (2b) has been converted in high yield by osmylation to the epimeric glycols 3 and 4 (R = H) which have been separated. This reaction proceeds with high chemoselectivity for reaction at the vinyl side chain but with low stereoselectivity, leading to a small excess of the 3-R isomer. Secologanin derivatives appear to show a much lower chemoselectivity in this reaction, but the stereoselectivity is considerably higher, and opposite to that in the sweroside example. Conditions have been found for oxidizing the dimethylacetal 5b of secologanin tetraacetate in useful yields to the epimeric glycols 6 and 7 (R = H); in this reaction a large excess of the 3-S isomer is formed. The reasons for these differences in selectivity appear to be related to differences between the two series in conformational preference.

Elimination reactions – Calculation of rate constants from equilibrium constants and distortion energies by means of no barrier theory

2005 ◽  
Vol 83 (9) ◽  
pp. 1654-1666 ◽  
Author(s):  
J Peter Guthrie ◽  
Leonardo Leandro ◽  
Vladimir Pitchko
Keyword(s):  
Free Energy ◽  
Alkyl Halide ◽  
Equilibrium Constants ◽  
Free Energy Of Activation ◽  
Carbon Carbon Bond ◽  
Alkyl Bromides ◽  
Encounter Complex ◽  
Leaving Group ◽  
Reaction Proceeds ◽  
Rms Error

No barrier theory has been applied to the E2 reactions of five alkyl bromides with ethanolic ethoxide. The model used for these reactions is that the reaction proceeds from the encounter complex of base and alkyl halide to the product encounter complex of halide ion and alkene (and alcohol), and requires five simple processes, which combine to give the concerted elimination: transfer of a proton from carbon to base; a change in geometry at the carbon which loses a proton from sp3 to sp2; breaking the C-leaving group bond; a change in geometry at the carbon which loses the leaving group from sp3 to sp2; and a change in the length of the carbon–carbon bond. The free energy of activation can be calculated with an rms error of 2.58 kcal mol–1 (1 cal = 4.184 J).Key words: Elimination, no barrier theory, rate constant, equilibrium constant.

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