This document summarizes research on the oxidation of alcohols using polymeric DABCO-bromine complex (PDB) and polyquinuclidinium bromine (BQBB). PDB and BQBB reactions were found to selectively oxidize secondary alcohols to ketones. PDB reactions proceeded faster and achieved higher yields in a biphasic CH2Cl2/H2O system compared to reactions using BQBB or PDB in other solvent systems. Allylic alcohols were oxidized more readily than benzylic or secondary alcohols by PDB, possibly due to complexation of the bromine by the benzyl group. Future work proposed exploring the use of these reagents to

1.
Rapid Regioselective Oxidations of Secondary Alcohols
with Polymeric DABCO-Bromine Complex (PDB)
Apryl Bronley-DeLancey
The University of Tampa
Department of Chemistry

2. What is oxidation?
The outcome of oxidation reactions of alcohols depends
on the substituents on the carbinol carbon.
In order for each oxidation step to occur, there must be
H on the carbinol carbon.
*http://www.chem.ucalgary.ca/courses/351/Carey/Ch15/ch15-4-6.html

3. Aldehydes and Ketones
H3C
C
CH3
O
H
C
H
O
Formaldehyde Acetone
Aldehydes must have at least one hydrogen
bound to the carbonyl carbon.
Ketones have two carbons bound to the
carbonyl carbon

4. •Primary alcohols can be oxidized to aldehydes or further to
carboxylic acids. In aqueous media, the carboxylic acid is usually the
major product. PCC or PDC, which are used in dichloromethane,
allow the oxidation to be stopped at the intermediate aldehyde.
*http://www.chem.ucalgary.ca/courses/351/Carey/Ch15/ch15-4-6.html
•Secondary alcohols can be oxidized to ketones but usually no
further
•Tertiary alcohols cannot be oxidized (no carbinol C-H)

5. *http://www.chem.ucalgary.ca/courses/351/Carey/Ch15/ch15-4-6.html

6. N
Br2
N NBr
Br2
CH2Cl2, 0o
C
+
-
Bisquinuclidiniumbromine(I) Bromide
"BQBB"
Hypervalent (10 e-
) bromine is a good source of "active bromine",
a mild oxidant.
Stable, decomposition resistant, yellow/orange solid.
Shown to be somewhat selective in oxidizing 2o
alcohols over 1o
alcohols
R R
OH
H
R H
OH
H
+
0.5 eqiv. BQBB
CH2Cl2/H2O R R
O
R H
OH
H
+
(1) "Selective oxidation of secondary alcohols by bis(quinuclidinium)bromine(I) bromide. A 2-coordinate
bromine(I) positive halogen reagent." Blair, L. K.; Bledsoe, R. K.; Burberry, K.; Struss, J. A., Unpublished.
(2) Blair, L. K.; Hobbs S.; Bagnoli, N.; Husband, L.; Badika, N. J. Org. Chem. 1992, 57, 1600.
“BQBB” Synthesis and Utility

7. R H
O
R
R R
O
H R
N R
R
-H+
+H+
R H
O
R
- R
N R
R
Br
+
R H
O
R
Br
R
N R
R
R
N R
R
H Br
Rate of reaction is slow in CH2Cl2; may rely on disassociation of BQBB
R
N R
R
Br
R
NR
R R
N R
R
Br
+
R
NR
R
Rates and yields are enhanced by running reactions in biphasic CH2Cl2/H2O
Rates enhanced by adding H+
catalyst (PPTS) or stochiometric amounts
of Ag+
(AgBF4).
Oxidations with BQBB

8. Alcohol Product Cat./
Reagent
Reaction
Times
Yield %
2-pentanol 2-pentanone AgBF4 5 min. 90
2,4-dimethyl-3-
pentanol
2,4-dimethyl-3-
pentanone
AgBF4 5 min. 100
cyclopentanol cyclopentanone PPTS 3 hrs. 97
2-pentanol 2-pentanone PPTS 3 hrs. 95
1-pentanol pentanal AgBF4 5 min. 65
1-octanol octanal AgBF4 5 min. 51
CH2Cl2/H2O (PPTS)
CH2Cl2 (AgBF4)
BQBB
R R'
H
R R'
OOH
Oxidations with BQBB

9. Polymeric DABCO Bromine Complex
NN N
2 Br2
NBr Br
CCl4, 25o
C
+
Polymeric DABCO Bromine Complex
"PDB"
N N
N
Hypervalent (10 e-
) bromine/Br3
-
is a good source of two equivalents of
"active bromine".
Ionic polymer, stable, decomposition resistant, yellow, insoluble solid.
Shown to be very selective in oxidizing 2o
alcohols over 1o
alcohols
Reactions are extremely slow (~4-80 hrs.) probably due to poor solubility.
Oxidations required additional DABCO.
Br3
-
2-4 equiv. DABCO
0.5 equiv. PDB, CH3CN, 25o
- 50o
C
R R'
H R R'
OOH

10. Alcohol Rxn. Time % Yield Ketone/
Aldehyde
% Mass
Balance
89 hrs 56% 91%
15.5 hrs 70% 95%
3 hrs 52% 100%
16 hrs 26% 80%
3.2 hrs 10% 81%
3.0 11% 77%
OH
OH
OH
OH
OH
CH3 CH2 CH2 OH
5
3 equiv. DABCO
CH3CN, 50o
CR R'
H
R R'
OOH 0.5 equiv. PDB
Blair, L. K.; Baldwin, J.; Smith, W. C. J. Org. Chem., 42, 1816, 1977.

11. Literature Summary
BQBB reactions involving "catalytic" PPTS employed 1.1 equivalents .
in biphasic CH2Cl2/H2O.
BQBB/AgBF4 reactions performed in the absence of H2O.
PDB reactions performed without catalysts or coreagents in the
absence of H2O.
PDB reactions required additional amine (DABCO) to aid reaction
and remove HBr as reactions progressed.

12. Explore catalyst loading for BQBB oxidations.
Mimic BQBB reaction conditions for PDB oxidations.
Use 2-pentanol as a basis system, then expand to other alcohols
and diols.
Explore the use of chiral amines to construct asymmetric oxidants.
Explore PDB and/or BQBB as oxidants to convert amines to
imines and/or aldehydes and ketones.
Research Objectives

13.
Catalyst Loading with BQBB
1.1 equiv. BQBBOH O
PPTS, CH2Cl2/H2O
2 hr.
Equiv. Catalyst Recovered
Alcohol
% Yield Ketone Mass Balance
1.1 27.8 83.4 111.2
0.5 29.0 78.2 107.2
0.25 22.8 81.6 104.4
0.1 26.5 76.7 103.2
.01 32.7 75.3 108.0
0 27.3 77.8 105.1
0 (no H2O) 94.8 7.3 102.1

14. OH
OH
OH
OH
OH
OH
OH
Recovered Alcohol:
% Yield Ketone:
Mass Balance:
19.9%
94.4%
114.3%
43.7%
21.1%
64.8%
0.0%
Quant.*
27.2%
65.5%
92.7%
24.1%
48.0%
72.1%
23.3%
63.6%
86.8%
37.5%
53.5%
91.0%
Recovered Alcohol:
% Yield Ketone:
Mass Balance:
- Reacts Rapidly
- Product May
React Further
CH2Cl2/H2O, 25o
C
0.55 equiv. PDB
R R'
H R R'
OOH
2 hr rxn time
With PDB. . . Just Add Water

15. OH
OH
OH
OH
OH
OH
Recovered Alcohol:
% Yield Ketone:
Mass Balance:
4.1%
93.9%
98.0%
0.0%
90.3%
90.3%
8.3%
84.9%
93.2%
0.0%
89.3%
89.3%
0.0%
83.9%
83.9%
3.2%
83.7%
86.9%
Recovered Alcohol:
% Yield Ketone:
Mass Balance:
CH2Cl2/H2O, 25o
C
0.55 equiv. PDB
R R'
H R R'
OOH
20 hr. rxn time
20 Hour Oxidations of Secondary Alcohols

16. CH2Cl2/H2O, 25o
C
0.55 equiv. PDB
R H
H R H
OOH
OH
OH
OH
OH
79.9%
8.7%
88.6%
63.3%
28.9%
92.2%
0.0%
97.1%
97.1%
84.3%
7.3%
91.6%
Recovered Alcohol:
% Yield Aldehyde:
Mass Balance:
2 hr. Oxidations
20 hr. Oxidations
67.1%
26.9%
94.0%
14.2%
85.3%
99.5%
0.0%
91.5%
91.5%
53.8%
44.0%
97.8%
Recovered Alcohol:
% Yield Aldehyde:
Mass Balance:
Oxidations of Primary Alcohols

17. OH
0.55 equiv. PDB
CH2Cl2/H2O, 25 o
C
15 min.
O
OH
0.55 equiv. PDB
CH2Cl2/H2O, 25 o
C
15 min.
O
No recovered alcohol!
Quantitative after 15 min.?
86.0 % recovered alcohol
9.6% yield
Allylic Alcohols vs. Benzyl Alcohols

18. Reactivity of Benzyl Systems
Piano stool complexes are common for many oranometallic complexes
h5 and h6 examples:
M
L
L
L M
L L
M
L
L
L
M
L L
Could the bromine(I) of PDB and BQBB behave similarly slowing
the rate of reaction?
For example:
Br
N N
OH

19. Metallic Bromine?!?!?
Can we synthesize the following complex to verify a previously undiscovered
metallic-like behavior of bromine?
Br
N NBr
-
- Na
+
BQBB
Na
+NaH
-H2
+
X-Ray crystallography studies of the cyclopenadienyl-BQBB complex should
verify the presence of the first bromine(I) piano stool complex.

20. Conclusions
BQBB oxidations do not require PPTS catalyst or co-reagents when
performed in biphasic CH2Cl2/H2O.
PDB oxidations are much faster in biphasic CH2Cl2/H2O compared to
CH3CN/DABCO system.
Rates of oxidation using PDB appear to favor allylic alcohols over
benzylic and secondary alcohols. The piano stool complexing
phenomenon may explain this behavior.
Oxidations appear to be very sluggish with primary alcohols.

21. Future Directions
R R'
NH2
H
[O]
R R'
NH
R R'
O
Active bromine complexes have been reported to oxidize amines to
ketones or aldehydes. Can the biphasic PDB system acheive this? .
Reports suggest an imine intermediate, yet the imine is not isolated.
If this oxidation works, can we stop at the imine?

22. Asymmetric BQBB-like Oxidants
N
N
TBSO
N
OTBS
N
Br
Br
-
N
N
TBSO Br2
2
N N
Br2 N N
Br
+
-Br
Can we construct asymmetric oxidants using sparteine or cinchona alkaloid
derivatives?
Sparteine reaction has been attempted: Very exothermic! Produces a thick .
orange semi-solid.
The reaction between quinidine derivative and bromine is low yielding.
None of these asymmetric oxidants have been characterized.

23. Acknowledgements
Matt DeLancey
W. David Barnhart
Mike Palmer (Sun Labs)
The University of Tampa (Delo Grant)
Dr. John Struss
Dr. Larry Blair (Berea College)
http://www.staff.livjm.ac.uk/pacfisma/cartlnk.html

24. The End