Download I (21 points) Complete the following reactions by providing starting

Name________________________________
Sp08_215_E1_p1
I (21 points) Complete the following reactions by providing starting material, reactants (number
steps as necessary), or products.
a) JOC 2008, 73, ASAP Kobayashi
O
1) OsO4
2) Na2SO3
N+
CH3 O
3
HO
O
THF, H2O
OH
b) JOC 2008, 73, ASAP Clayden
O
O
CH3
N
O
N
H
3
N
H
N
CH3
OH
3
c) Org. Lett. 2008, 10, 1807
1) CH3CH2CH2CH2Li (base)
O
H
O
OCH3
2)
[(CH3)2CH]3Si
O
H3C
3) protonation
3
d) JOC, 2008, 73, ASAP Mandal
H3C
HO
I
PhCH2O
H
O
O
O
NaH
+ NaI + H2 3
e) Org. Lett. 2008, 10, 1679
HS
HCl
intramolecular hemiacetal w/ 4-hydroxy
SH
HO
HO
H
H
S
S
OH
+ H2O
3
O
H
cat. acid
C15H20O3S2 including 3
6-membered rings
+ H2O
3
Name________________________________
Sp08_215_E1_p2
II (30 points)
A. (JOC 2008, ASAP, Hartung) The reagent 2-chloro-bis[menth-1-yloxycarbonyl]-1,3,2dioxaphospholane was shown to be useful in determining the enatiomeric purity of chiral alcohols
via 31P NMR. The enatiomerically pure phosphorous reagent reacts with chiral alcohols to form
diasteromers as shown below. The phosphorous diastereomers have baseline-separated signals.
Circle the appropriate stereochemical designation for each stereocenter below.
R or S
R or S
H
R or S
H
O
H
O
O
O
O
OH
P Cl
H
O
Ph
H
O
O
O
R or S
O
O
O
H
H
H
P O
Ph
R or S
10
2-chloro-bis[menthy-1-yloxycarbonyl]1,3,2-dioxaphospholane
In the meso form of 2-chloro-bis[menth-1-yloxycarbonyl]-1,3,2-dioxaphospholane how many of
the eight stereocenters would have the opposite configuration from that shown above? (Circle
the correct number below)
0 (it is meso as drawn) 1
2
3
4
5
6
7
8
2
B. (Org. Lett. 2008, 10, 1715) The following transformation was carried out. Fill in the oxidation
numbers of the atoms indicated below.
How many of the atoms in the aromatic ring were
O
OCH3
oxidized? (Circle the correct number)
5 steps
NH
N
0
1
2
3
4
5
6
N
N
O
N OCH3
H
How many of the atoms in the aromatic ring were
O
reduced? (Circle the correct number)
0
1
2
3
4
5
6
6
6
C. Provide the IUPAC name for the following molecules
H
HO
H3CO
O
OH
H
H
6
Name________________________________
Sp08_215_E1_p3
III (24 points)
A. (JOC 2008, ASAP, Shaabani) "The following reaction includes some important aspects like the
use of water as a reaction component and a 'green' reaction medium, high atom economy, and mild
reaction conditions."
O
O
NC NH2
TsOH
2
+
N
C
+
H
O
+
2
NH
NH HN
16-24 hr
NC NH2
2,3-diaminomaleonitrile
NC CN
The authors propose a multistep mechanism that begins with the "formation of diimine 6 from
condensation between DAMN and ketones." DAMN is 2,3-diaminomaleonitrile.
NC
NH2
+ 2 O
NC NH2
2,3-diaminomaleonitrile
NC
N
NC
N
+ 2 H2O
diimine 6
Show the mechanism of formation of one of the imines. Use HB as the catalytic acid and B- as
its conjugate base.
NC
NH2
+
NC
O
H-B
NH2
NC
N
NC
NH2
monoimine
18
B. Provide the IUPAC name for the following molecule:
HO
OH
O
6
Name________________________________
Sp08_215_E1_p4
IV (24 points)
A. (JOC, 2008, ASAP, Loh) Chemists have been studying the Barbier-Grignard reactions with the
goal of affecting the carbon-carbon bond forming reaction in solvents like water. Recent
developments include the use of indium metal catalysts that react through single electron transfer
mechanisms. Show the product of the following reaction:
i)
O
In/CuI/I2
1) Mg
+
OR
I
H
H2O, 2 days
2) protonation
3
ii) The indium catalyst is also very effective for coupling cyclohexyl iodide with
4-bromobenzaldehyde as shown below. Why would the Grignard reagents [1) Mg + 2)
protonation] be a poor choice for this coupling reaction? (Use structures of possible products
and words to explain.)
O
1) Mg
???
I
H +
2) protonation
Br
5
B. (JOC, 2008, 73, 2592) The authors of this paper were studying the biosynthesis of 1,1dihalogenated 1-alkenes via an anti-periplanar E2 elimination of HBr using 1,1-dibromo-1-chlorobutane as their model. The products of the elimination reaction are diastereomers. Draw them:
i)
Cl
ii)
+
E2 elimination of HBr
Br Br
Z-isomer
E-isomer
4
Draw Newman projections of the three possible staggered conformers of
1,1-dibromo-1-chlorobutatne looking at the first carbon down the C1-C2 bond.
iv)
iii)
vi) Which conformer
leads to the Z-isomer?
(Circle one)
v)
X
Y
Z
3
Conformer X
3
Conformer Y
3
Conformer Z
3
Name________________________________
Sp08_215_E1_p5
V (21 points)
(JOC, 2008, ASAP, Li) The authors of this paper describe an acid catalyzed intramolecular Friedel
Crafts Alkyation. A key intermediate in the reaction mechanism is the carbocation resulting from
the loss of water. Product A is the only product. The carbocation intermediate leading to product B
does not form due to the steric interactions.
I
I
H2SO4
I
OH
Product A
Product B
a) Draw the three major resonance contributors of this carbocation intermediate:
(rotation around a C-C bond may lead to one or more of the resonance contributors)
Resonance contributor
leading to Product A
Resonance contributor
leading to Product B
9
b) The reaction rates were correlated with the predicted relative stability of the corresponding
carbocations; rank the expected order of carbocation stability. Start with the least stable
carbocation. Briefly explain your ranking.
OCH3
I
OH
Alcohol A
least stable
carbocation derived
from A-D
I
I
OH
Alcohol C
Alcohol B
<
OH
<
<
I
OH
Alcohol D
most stable
carbocation derived
from A-D
Briefly explain your ranking
12