13C lithiation shifts in aldimines and ketimines. Evidence on the configuration of lithiated N-tert-butylimines

1981 ◽  
Vol 59 (20) ◽  
pp. 3007-3011 ◽  
Author(s):  
Robert R. Fraser ◽  
Noemi Chuaqui-Offermanns
Keyword(s):  
Alkyl Group ◽  
Tert Butyl

The 13C shieldings for a series of aldimines and ketimines have been measured along with the shifts for their 1-lithio derivatives. For those aldimines with a primary or secondary alkyl group attached to nitrogen, the "lithiation shifts" for the attached carbon (C-4) were all upfield due to the change from anti to syn configuration on lithiation. In the ketimines and in the N-tert-butyl aldimines and ketimines, the lithiation shifts for the C-4 carbon failed to provide stereochemical information. The shifts at C-1 and C-2 proved similar to those previously observed for lithiated alkenes.

Infrared Study of Alkyl Isothiocyanates in Carbon Tetrachloride and/or Chloroform Solutions

1993 ◽  
Vol 47 (6) ◽  
pp. 677-686 ◽  
Author(s):  
R. A. Nyquist ◽  
C. W. Puehl
Keyword(s):  
Carbon Tetrachloride ◽  
Alkyl Group ◽  
High Frequency ◽  
Fermi Resonance ◽  
Methyl Ethyl ◽  
Infrared Study ◽  
Tert Butyl ◽  
Electron Donation ◽  
Hydrogen Bonded

The νasym.NCS frequencies for alkyl isothiocyanates occur at higher frequency in CHCl3 or CDCl3 solution than in CCl4 solution. The νasym.NCS mode increases in frequency as the mole % CHCl3/CCl4 increases. The νasym.NCS mode for butyl isothiocyanate occurs at an exceptionally high frequency, and this result is explained in terms of the formation of a pseudo-six-membered intramolecularly hydrogen-bonded ring. The νasym.NCS modes for the alkyl isothiocyanates are corrected for Fermi resonance (FR), with the exception of the propyl analog. The propyl analog appears to have three other modes in FR with νasym.NCS, and an equation has not yet been developed to correct for FR in this case. The unperturbed νasym.NCS frequencies for alkyl isothiocyanates decrease in the alkyl order: methyl, butyl, ethyl, and tert-butyl. The decrease in frequency of νasym.NCS in the order methyl, ethyl, and tert-butyl isothiocyanate is attributed to weakening of the N=C=S bonds due to σ electron donation of each alkyl group. In the case of the butyl analog, the σ electron donation is partially compensated for by the postulated existence of a pseudo-six-membered hydrogen-bonded ring.

Synthesis of optically active l-acyl-2-O-alkyl-sn-glycero-3-phosphocholine via 1-O-benzyl-sn-glycerol 3-arenesulfonate

1990 ◽  
Vol 68 (1) ◽  
pp. 360-365 ◽  
Author(s):  
Shaukat Ali ◽  
Robert Bittman
Keyword(s):  
Benzyl Alcohol ◽  
Alkyl Group ◽  
Boron Trifluoride ◽  
Enantiomeric Excess ◽  
Boron Trifluoride Etherate ◽  
Optically Active ◽  
Epoxide Ring ◽  
Phospholipid Synthesis ◽  
Tert Butyl ◽  
Very High

A stereocontrolled route to 1-palmitoyl-2-O-hexadecyl-sn-glycero-3-phosphocholine from (R)-glycidyl tosylate is described. This method gives very high enantioselectivity (93–96% enantiomeric excess) and can be used to prepare 3-acyl-2-O-alkyl-sn-glycero-1-phosphocholines from (S)-glycidyl tosylate. The key step is the preparation of 1-O-benzyl-sn-glycerol 3-tosylate by the boron trifluoride etherate catalyzed regio- and stereo-specific opening of the epoxide ring with excess benzyl alcohol. The alkyl group is introduced using alkyl trifluoromethanesulfonate in the presence of excess 2,6-di-tert-butyl-4-methylpyridine. Debenzylation gives 2-O-alkyl-sn-glycerol 3-arenesulfonate, which is acylated and then converted into the phosphocholine. The use of chiral glycidyl derivatives as starting materials for the synthesis of glycerophospholipids is discussed.Key words: acylalkylglycerophospholipids, phospholipid synthesis, glycidyl derivatives in phospholipid synthesis, epoxides as precursors of phospholipids.

1,4-Addition of Lithium Organyls to para-Quinols / Structure Determination of 2,6-Di-tert-butyl-4-hydroxy-4,5-diphenylcyclohex-2-en-1-one

1996 ◽  
Vol 51 (3) ◽  
pp. 381-387
Author(s):  
Gerhard Henes ◽  
Anton Rieker ◽  
Markus Neumayer ◽  
Wolfgang Hiller
Keyword(s):  
Nmr Spectroscopy ◽  
Structure Determination ◽  
Alkyl Group ◽  
Boat Conformation ◽  
X Ray ◽  
Organic Group ◽  
Tert Butyl ◽  
Cyclohexene Ring ◽  
Twist Boat

Abstract Addition of lithium organyls to sterically hindered para-quinols leads to 1,2-or 1,4-adducts. The 1,4-addition prevails, if the 4-substituents in the quinol and the organic group in the lithium organyl are large. Four 1,4-addition products (2-cyclohex-2-en-1-ones) are synthesized and their structures investigated by NMR spectroscopy. The aryl groups at C-4 and C-5 acquire equatorial positions, the alkyl group at C-6 is bisectional. These results are confirmed by X-ray analysis of 2,6-di-tert-butyl-4-hydroxy-4,5-diphenylcyclohex-2-en-1 -one, revealing a twist boat conformation of the cyclohexene ring.

Unprecedented 1,3-tert-butyl migration via the C–N single bond scission of isonitrile: an expedient metal-free route to N-sulfonyl amidines

2020 ◽  
Vol 56 (60) ◽  
pp. 8408-8411
Author(s):  
Debashish Mishra ◽  
Arun Jyoti Borah ◽  
Pinakinee Phukan ◽  
Debojit Hazarika ◽  
Prodeep Phukan
Keyword(s):  
Alkyl Group ◽  
Single Bond ◽  
Metal Free ◽  
Tert Butyl ◽  
Bond Scission ◽  
And Migration

Treatment of tert-butyl isonitrile with ArSO2NBr2 and nitrile led to simultaneous C–N single bond scission of isonitrile and migration of tert-alkyl group to nitrogen centre of the nitrile precursor, resulting in the formation of N-sufonyl amidine.

Dipole moments induced in larger molecules. Triphenylmethyl derivatives

1982 ◽  
Vol 47 (6) ◽  
pp. 1733-1737 ◽  
Author(s):  
Otto Exner ◽  
Dario Iarossi ◽  
Piero Vivarelli
Keyword(s):  
Functional Groups ◽  
Quantitative Evaluation ◽  
Alkyl Group ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Phenyl Group ◽  
Benzene Derivatives ◽  
Tert Butyl

Dipole moments of triphenylmethyl derivatives I-VI with electron attracting functional groups were measured in benzene solution. Comparison with respective methyl and tert-butyl derivatives revealed the moments induced in the phenyl group which are possibly somewhat greater than those induced in an alkyl group. These moments should be accounted for when determining mesomeric dipole moments of acceptor groups from benzene derivatives; however, a quantitative evaluation is not yet possible.

Control of the orientation of the aldehyde group in 2-(alkylthio)benzaldehydes by the directional lone-pair on sulfur

1985 ◽  
Vol 63 (3) ◽  
pp. 777-781 ◽  
Author(s):  
Ted Schaefer ◽  
Glenn H. Penner ◽  
Kerry J. Davie ◽  
Rudy Sebastian
Keyword(s):  
Chemical Shift ◽  
Alkyl Group ◽  
Lone Pair ◽  
Aldehyde Group ◽  
Ring Plane ◽  
Spectral Parameters ◽  
Tert Butyl ◽  
H Nmr ◽  
Lone Pairs ◽  
Repulsive Interactions

The 1H nmr spectral parameters for 2-alkylthio derivatives benzaldehyde (alkyl = CH3, CH2CH3, CH(CH3)2, C(CH3)3) are used to show that the O-syn conformation of the aldehyde group decreases from 40% for the methyl to zero for the tert-butyl compound in CC14 solution at about 300 K. It appears that the alkylthio groups twist out of the benzene plane to the same extent as in the alkyl phenyl sulfides and that it is the concomitant approaches of the 3p lone-pairs on sulfur into the ring plane which, by repulsive interactions with the C=O bond, determine the conformations of the aldehyde group. The spectral parameters display interesting changes as the size of the alkyl group increases. For example, the chemical shift of the aldehydic proton is larger than that reported for any other benzaldehyde derivative in CCl4 solution.

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