The reactions of simple dimethylallylamines with dimethyl acetylenedicarboxylate. Formation of 1-dimethylamino-2-allylmaleates via formal allyl transfer

1988 ◽  
Vol 66 (7) ◽  
pp. 1686-1694 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Carbonyl Group ◽  
Quaternary Ammonium ◽  
Methyl Groups ◽  
Dimethyl Acetylenedicarboxylate ◽  
Tertiary Amines ◽  
Reversible Formation ◽  
Zwitterionic Intermediate ◽  
Membered Transition State

Tertiary amines bearing two methyl groups and an allylic substituent (X) react with dimethyl acetylenedicarboxylate (DMAD) to afford the corresponding 1-dimethylamino-2-X′ maleates, in which X′ is the allylic isomer of X. The mechanism postulated involves reversible formation of a zwitterion by attack of the amine at an sp-carbon of DMAD. The zwitterion then undergoes intramolecular allyl transfer, through a 6-membered transition state. Evidence for a zwitterionic intermediate (quaternary ammonium allenolate) includes capture of the allenolate centre by intramolecular addition to a carbonyl group and by proton transfer from chloroform.

Ion-Cyclotron Resonance Studies of Alkylsilyl Ions. I. The Reactions Between Alcohols and the Trimethylsilyl Cation

1979 ◽  
Vol 32 (1) ◽  
pp. 59 ◽  
Author(s):  
IA Blair ◽  
G Phillipou ◽  
JH Bowie
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Cyclotron Resonance ◽  
Nucleophilic Attack ◽  
Ion Cyclotron Resonance ◽  
Trimethylsilyl Cation ◽  
Ion Cyclotron ◽  
Decomposition Pathway ◽  
Membered Transition State

Nucleophilic attack of an alcohol (ROH) at the electrophilic silicon centre of the trimethylsilyl cation (Me3Si+) produces the 1 : 1 adduct Me3-O+(H)R(1). The adduct may fragment by loss of methane to yield Me2Si+-O-R; and this elimination is most pronounced when R = Me. When R ≥ C2H5, the major decomposition pathway of (1) involves elimination of the alkene [R-H] to produce Me3Si-O+H2, which may undergo further reaction with the neutral alcohol to reform (1). The proton transfer which accompanies the elimination of [R- H] from (1) originates predominantly from C2 of the alcohol; this suggests the intermediacy of a four-membered transition state in this reaction.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

Ionic dimerisation of trifluoropropenenitrile and its addition reactions with methyl trifluoropropenoate

1980 ◽  
Vol 45 (2) ◽  
pp. 406-414 ◽  
Author(s):  
Jiří Svoboda ◽  
Oldřich Paleta ◽  
Václav Dědek
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Substituent Effect ◽  
Solvent Molecule ◽  
Addition Product ◽  
Potassium Fluoride ◽  
Relative Reactivity ◽  
Addition Reactions ◽  
Tertiary Amines ◽  
Optimum Conditions

Dimerisation of trifluoropropenenitrile (I) in the presence of potassium fluoride and tertiary amines afforded a mixture of stereoisomeric perfluoro-4-methyl-pentenedinitriles (II), higher-boiling compounds, and 2,3,3,3-tetrafluoropropanenitrile (III) which arises by proton transfer from the solvent molecule. Under optimum conditions, product II was obtained in about 50% yield. Reaction of the nitrile I with methyl trifluoropropenoate (IV) gave, besides the dimers II and V, the product of addition of the nitrile I to the propenoate, IV, i.e. methyl 4-cyanoperfluoro-2-pentenoate (VI), and the addition product of the propenoate IV to the nitrile I, i.e. methyl 4-cyanoperfluoro-2-methyl-3-butenoate (VII). The relative reactivity if I and IV is discussed. The ratio of stereoisomers in II, V, VI and VII indicates that the magnitude of the steric substituent effect, operating in the reaction mechanism, decreases in the order -CFCF3.(COOCH3) > -CFCF3(CN) > -COOCH3 > -CN.

scholarly journals Formation of N-Nitrosodimethylamine from Naturally Occurring Quaternary Ammonium Compounds and Tertiary Amines

Nature ◽  
1972 ◽  
Vol 236 (5345) ◽  
pp. 307-307 ◽  
Author(s):  
WALTER FIDDLER ◽  
JOHN W. PENSABENE ◽  
ROBERT C. DOERR ◽  
AARON E. WASSERMAN
Keyword(s):  
Quaternary Ammonium ◽  
Quaternary Ammonium Compounds ◽  
Tertiary Amines ◽  
Naturally Occurring ◽  
Ammonium Compounds

ChemInform Abstract: TRANSITION-STATE PLIABILITY IN NITROGEN-TO-NITROGEN PROTON TRANSFER

1983 ◽  
Vol 14 (33) ◽  
Author(s):  
F. M. MENGER ◽  
J. GROSSMAN ◽  
D. C. LIOTTA
Keyword(s):  
Proton Transfer ◽  
Transition State
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