Transformation of Formaldehyde Aminals into Diaminocarbenes and Carbeniurn Salts

148 Pages·2001·5.99 MB·English

Transformation of Formaldehyde Aminals into Diaminocarbenes
and Carbeniurn Salts
by
José M. Rodezno
A thesis submitted in conformity with the requirements
for the Degree of Master of Science, MSc.,
Department of Chemistry,
University of Toronto
O Copyright by José M. Rodezno, 2001
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Fie: Transformation of Fomaldehyde Aminals into Diaminocarbenes and Carbenium Salts
Degree: Master of Science, MSc.
Year of convocation: 2001
Author: Jose M. Rodezno
Department of Chemistry, University of Toronto
Abstract
The reactivities of the two stable diaminocarbenes 1, 3-di-tert-butyl-irnidazole-2-
ylidene 1 and 11 3-di-tert-butyl-imidazolidine-2-ylidene2 toward hydrogen, oxygen, water
and carbon monoxide and SOg were investigated. Contrary to comrnon belief the
deterioration of 1 and 2 is not due to oxidation by triplet oxygen, but is the result of
hydrolysis. The hydrolysis rate ab room temperature is very low for the aromatically
stabilized 1 but very rapid for the non-arornatic 2. The reactions are not acid or base
catalyzed. Computational data show that the reaction with triplet oxygen is only kinetically
hindered and that the oxidation of 1 and 2 to the respective ureas is in fact strongly
exothermic. Both carbenes insert into dihydrogen only in the presence of hydrogenation
catalysts. Carbene 2 foms a 1: 1 adduct with S02 that is best described as a Lewis adduct
The ammatic ring protons in 1 undergo rapid deuteiium - hydrogen exchange n
DMSO-d6, CD30D and D20. The oxidation of aminals by oxidizing agents like N BS,
NCS, CC14, CBr4. 12 or CuC12 leads to diaminocatbenium salts in high yields. These
oxidations c m be extended to 1,3,5-triazacyclohexane R3TAC systems, to give the
monocaüonic sak [R3TAC] [XI. The carbene, 1,3,5-tri-tert-butyl-l,3,5-triazacycloh exane-
2-ylidene 9, derived through deprotonaiion of the [R3fAC][Br] has been observed n
benzene-d6 solutions. Reaction of R3TAC with CuCI2 leads to metal-1,3,5-
triazacyclohexane complexes.
For Lisa
"We are here for this - to make rnistakes and to corredourselves, to stand the blows and
hand thern out." Primo Levi.
III
Acknowledgements
First and foremost 1 would like to express my sincere gratitude to Prof. Michael Denk,
who introduced me to one of the most exciting fields of chemistry.
To ail those who ai someway or another have helped me 1 am dso grateful. h
W*cuI, I would like to thank Dr. Garnil Aihakirni for çtirnulating discussions, Sébastien
Fournier and former group mernbers Liça H. Studnicki (pobie) and John H. Brownie.
1 must also thank Dr. Alan Lough, who I bothered throughout the course of two years
with pseudo-crystals, along with Dr. Tim Burrow and Dr. Paul Isbester (York University) for
NMR spectroscopy and Dr. Alex Young for mass spectrai analysis.
Finally, I would like to thank my family for ail the support provideci.
List of Abbreviations
A Angstrom (10 -10 m)
Ad Adamantyl
Ar Aryl group
boiling point
bp
br broad
cm-' cetimetre inverse (1 R)
d doublet (NMR)
dd double of doublets (NMR)
DMSO Dimethylsulfoxide
S denotes chernical shift (NMR)
A denotes high temperature
AH reaction enthaipy
E ~ I Electronic Energy
Et Ethyl
Thermal Energy
Eth
El-MS Electron Impact Mass Spectrum
ES-MS Electrospray Mass Spectrum
R-IR Fourier-Transfomi lnfrared Spectroscopy
9 Q-
-
GC-MS Gas Column Mass Spectroscopy
h hair
ipr iso-Propyl
J Coupling constant
LH2 (CH3)3C-N(H)-CH2-CH2-N(H)-C(GH3)3
L' (CH3)3C-N=CH-CH=N-C(CH3)3
LDA Lithium Diisopropylamine
m multiplet (NMR); or medium (IR); or meta position
v
Me Methyl
Mes Mesityl
MHz Megahertz
mL millilitre
mmol millimole
m/z mass to charge ratio (MS)
mol mole
melting point
mP
MS Mass Spectroscopy
NBS /Ubromosuccinirnide
NCS Nd-ilorosuccinimide
NMR Nuclear Magnetic Resonance
Hz Hertz
ortho
O
P Para
Ph Phenyl
PPm parts per million
qr quartet (NMR)
qn quintet (NMR)
rel. int. % percent relative intensity
r.t room temperature
s singlet (NMR); strong (IR)
Sb subvalent compound
t triplet (NMR)
TAC 1,3,5-Triazacyclohexane
tBu tertiary-Butyl
tert terh'ary
THF Tetrahy drofuran
TMS Tetramethylsilane
U wavenumbers
v ve'Y
weak (IR)
W
X halogen
ZPE Zero Point Energies
Table of Contents
..........................................................................................
........... ..................................................................................
Carbenes
..,
Origins of Diaminocarbene Chemistry. ........... .... ...........................
WanziicKs Contributions ................. ... ...............................................
...........................................................
Electronic Structure of Carbenes
Influence of Substituent on the Electronic Structure of Carbenes. .....
Electronic Effects. ........... ......... . ...........................................................
............................................................................................
Steic Effects
Synthesis of Stable Carbenes. ........................... .... .............................
Structure of Stable Carbenes. ............ .. .............................................
.................................................................
Diaminocarbene Congeners
Starting Materiais for the Synthesis of Diaminocarbene. ....................
Carbenium Cations. ...................... .. ..................................................
lonic Liquids. ..........................................................................................
Thioureas. ................................................. ...... ......................................
. .
..............................................................................
Research Objectives
Chapter 2: Resuits and Discussion. .....................................................................
..............................................................
2.1 Oxidation of Diaminocarbenes
2.2 "Air Sensitivity" of Diaminocarbenes. .................................................
..........................................................
2.3 Oxop hiiicily of Diaminocarbenes
2.4 Deuterium Labeling of I,3-Di-fert-butylimidazole- 2-ylidene. .............
2.5 Formation of a Diaminocarbene-S02 Adduct ......................................
....................................................................
2.6 Reactions with CO and H2
2.7 Synthesis of Carbenium Salts .................... .... ................................
.........................................................................
2.8 Thauer's Hydrogenase
Synthesis of 1.3.Di.tert.butyl.3.4.5. 6.tetrahydropyrhkhe-Z
yiidene ........................................ .. ........................................................ 47
.....................................................................
1, 35,.T riazacyclo hexanes 48
Synthesis of lI3,5.Tri.ted4utyl-1,3, 54riazacyclohexyl Cahenium
..............................................................................
Cation [tBu3TAC]M 49
Deprotonation of 1,3,S.Tri4ert-butyl4,3, 5.triazacyclohexyl
Carbenium Bromide rBu3TAC][Br]. ......................... .. ......................... 51
Attempted Synthesis of 1,3,5.Tri4ert.butyl.l,3, 5.triazacyclohexyl
triscarbenium Cation PBu3TAC]k]. ....... . .. .. ............................... 52
1,3,5.Tri~tert.butyl.l, 3,5.triazacyclohexan e.CuCh Adduct ............... 53
Chapter 3: Expairnenta l ....................................................................................... 56
...............................................................................
Expimental Notes 57
Preparation of Compounds ........................ .. ...................................... 58
Preparation of 1,3.Di~tert.butylirnidazole. 2.ylidene (1 ) .................. .... 58
Preparation of 1,3~Di.tert~butyl.imidazolidine2.. ylidene (2) ............... 59
Preparation of 1.3.Di.tert-butyl.3.4.5.64etrahydropyrimidine. 2.
.................................. ... ..........................................................
yiidene (3) 60
Preparation of 1.3.Di.tert~butyîimidazolidine. 24hÏone (2=S) ............. 61
Preparation of 1.3.D i. tert-butylimidazole-2-thione (1= S) ................... 62
Preparation of 13-Di-t ert-butylimidazole-2-one (1= O)... ................... 63
Preparation of 1.3~Di~tert~butylimidazolid2.ionnee ~ (2=0)... ............. 64
Preparation of 1.3~Di4ert~butylimida~olidine~2~thiSo-ndeio~xSid.e
(2-SQ) ....................................... .. .......................................................... 66
Preparation of 1.3.Di.tert. butylimidazolidine (2-Hz). .......................... 66
...........................
Preparation of 1. 3.Diphenylimidazolidine (2Ph-H2) 67
Preparation of 1. 3=Dimethylimidazolidine( 2Me.Hz) ........................ 68