Post on 17-Mar-2020
Topic ReviewIevgeniia Kovalova
14. 04. 2016
Catalytic,StereoselectiveDihalogenationofAlkenes
Cresswell,A.J.;Eey,S.T.-C.;Denmark,S.E.Angew.Chem.,Int.Ed.2015,54,15642
2
Introduction
C C
X
R1
R2
R3
R4
C CR1
R2
R3
R4
Br Br C CR1
R2
R3
R4
BrBr
δ+
δ-
π-complex
C C
Br
R1
R2
R3
R4
Br
C C
X
R1
R2
R3
R4
Roberts,Kimball,jacs,1937,59,946Robinson,InstituteofChem.OfGreatBritainandIreland,1932
3S.A.Snyder, Z.-Y.Tang, R.Gupta, J.Am.Chem.Soc.2009,131, 5744–5745
Enantioselective alkenedihalogenation insynthesisofnaturalproduct
O
O
O
OH
MOMO MeMe
O
O
O
OH
MOMO MeMe
ClCl
OBH
OO
O
O
OH
HO MeMeClCl
(-)-napyradiomycin
chiral additive(4 equiv)
THF, rt, 1hthen Cl2CH2Cl2
-78 ˚C, 20 min
93%, 93.5:6.5 er(97.5:2.5 er after recryst.)
chiral additive
4S.A.Snyder, Z.-Y.Tang, R.Gupta, J.Am.Chem.Soc.2009,131, 5744–5745
O
O
O
OH
MOMO MeMe
ClCl
O
O
O
OH
MOMO MeMe
5K.C.Nicolaou, N.L.Simmons, Y.Ying, P.M.Heretsch, J.S.Chen, J.Am.Chem.Soc. 2011,133, 8134–8137
Cl
OHCl
Cl
OHClMe
Cl
OHClCl
63%, er=90.5:9.5 65%, er=72:28 81%, er=85.5:14.5
Enantioselective, catalyticalkenedihalogenation
R2
R1 OH
4-Ph(C6H4)ICl2 (1.6 equiv)
(DHQ)2PHAL (20 mol %)CH2Cl2 (0.05 M)
-78 ˚C
R1 OHCl
R2 Cl
N
MeO
ON N
H
Et
N
OMe
ONN
Et
H
(DHQ)2PHAL
Ph
I ClCl
4-Ph(C6H4)ICl2
Cl-agentcatalyst
6
7
EtO
O
OEt
O
Br Br
R Ar
unreactive Br+ sourse
EtO
O
OEt
O
Br Br
Me*L Br
δ+
δ−
R Ar
Br
Br
Chiral ligandL*
Br- sourseM Br
enantioenriched dibromides
EtO
O
OEt
O
Br Br
HO Ph HO PhBr
Br
O
O OHOH
2-NpNp-2
Np-2 2-Np
(1.5-2.0 equiv.) (20-100 mol%)
BrTi(Oi-Pr)3 (1 equiv)
2:1 MeCN/Tolrt, 12-60h
D.X.Hu, G.M.Shibuya,N.Z.Burns, J.Am.Chem.Soc. 2013,135, 12960–12963
OH
Br
Br
20 mol % of diol: 60%, ee=76%100 mol % of diol: 63%, ee=86%
OH
Br
Br
20 mol % of diol: 47%, ee=79%100 mol % of diol: 65%, ee=88%
F
OH
Br
Br
20 mol % of diol: 60%, ee=85%100 mol % of diol: 64%, ee=90%
Cl
OH
Br
Br
20 mol % of diol: 51%, ee=84%100 mol % of diol: 64%, ee=90%
Br
Enantioselective, catalyticalkenedibromination
8D.X.Hu, G.M.Shibuya,N.Z.Burns, J.Am.Chem.Soc. 2013,135, 12960–12963
HO Ph
OH
BrTi(Oi-Pr)3+
EtO
O
OEt
O
Br Br
+
3 i-PrOH
EtO
O
OEt
O
Br Br
Ti O
∗
PhBrO
O
OH
∗
EtO
O
OEt
OTi O
PhBrO
O
∗
Br
Br
EtO
O
OEt
OTi OBrO
O
∗
Br
BrPh
HO Ph
Br
Br
O
O OEt
Br
OEt
Ti(i-PrO)3
+
δ+
δ−
9D.X.Hu, F.J.Seidl,C.Bucher,N.Z.Burns,J.Am.Chem.Soc.2015,137,3795−3798
R2
R3
HOR1
R2HO
NBS (1.05 equiv)ClTi(Oi-Pr)3 (1.1 equiv)
13 (10-30 mol %)
hexanes-20 ˚C, 4-12 h
N
O
O
Br
NBS
N
HOt-Bu
t-Bu
OH
PhPh
13
R3
ClR1
Br
(chiral catalist)
(S)(R)
PhHO
88%, ee=89%, cr >20:1
PhHO
94%, ee=89%, cr=8:1
PhHO
89%, ee=92%, cr=18:1
ClCl
Me
Cl
Br
Br
Br Me
Br
ClHO
86%, ee=94%, cr=6:1
Enantioselective, catalyticalkenechlorobromination
10
OH
BrMe
OTi
LnClBr
Me OTiLn
Cl
NBS, ClTi(Oi-Pr)3
20 mol%(R,S)-13
20 mol%(S,R)-13
OH OH
BrCl
Br Cl
(S)-perillyl alcohol95%, cr=17:1 88%, cr>20:1
OH
NBS, ClTi(Oi-Pr)320 mol% (R,S)-13
hex, -20 ˚C OH
BrCl
DMP, NaHCO3
BrCl
O
H
BrCl
Ph3P=CH2
(+)-bromochloromyrcene
11
Me Me
Me
OH
Me Me
OH
NBS, (1.05 equiv)BrTi(Oi-Pr)3 (1.10equiv)
13 (20 mol%)
hex, -20 ˚C
Br
MeBr
Me Me
Me
OH Me Me
OHBr
BrMe
NBS, (1.05 equiv)BrTi(Oi-Pr)3 (1.10equiv)
13 (20 mol%)
hex, -20 ˚C
74%, 92% ee
78%, 95% ee
Ph OHPh OH
ClCl
t-BuOCl (1.05 equiv)ClTi(Oi-Pr)3 (1.10 equiv)
13 (30 mol%)
hex, -20 ˚C61%, 90% ee
12
X XXX X X+
moleculardihalogen
separate halenium and halide equivalents
dihalogen equivalent
Dihalogenating Reagents
R2
R1 R3
R4 BrR2
R3R4
R1Br
1 2
1 + 2NaBr + 1/2 Na2[B2(O2)2(OH)4] 2 Na3BO3 + H2O
1 + ZnBr2 + Pb(OAc)4 2 + Zn(OAc)2 + Pb(OAc)2
K.W.Rosenmund,W.Kuhnhenn,Ber.Dtsch.Chem.Ges. 1923,56, 1262–1269T.Schlama, K.Gabriel, V.Gouverneur, C.Mioskowski,Angew.Chem.Int.Ed.Engl.1997,36, 2342–2344
NH
Br3
Et4N+ Cl3-
Mioskowski's reagentslow release of Cl2 on storage
[R4N]+[(X2)nX]-
13
X
acid H +
X
acid H
δ+δ−
acid Xδ− δ+
+
H
acid
X
+ acid
Xδ− δ+
base + X base Xδ−δ+
base +X
PTCorganic phase
aqueousor solid phase
substrate
X
Brønsted acid
Lewisacid
Lewisbase
Phasetransfer
Catalysisproblem
14
Brønsted acidcatalysis
Brønsted acidcatalyzedalkenedihalogenation usingseparateX+andX-sources
acid HX
X
acid H
δ+δ−
δ−
H
acid Xδ− δ+
+
XX2
acid H
-
-
R2R1
HR2R1X
acid
acid
XR1
XR2
X
H
δ+δ−
15
Brønsted acidcatalysis
Brønsted acidcatalyzedalkenedihalogenation usinganX+reagentcombinedwithacomplexanionofthehalideasanX- sources
acid HX
X
acid H
δ+δ−
δ−
H
acid Xδ− δ+
+
R2R1
HR2R1X
acid
acid
X-MXnR1
XR2
X
H
δ+δ−
+ MXn
MXn
16
Brønsted acidcatalysis
Brønsted acidcatalyzedalkenedihalogenation usingadihalogenequivalentasasinglereagent
acid HX
X
acid H
δ+
δ−δ−
R2R1
R2R1X
R1
XR2
X
X
X
acid H X
+
X2
acid H-
-
17
Lewisacidcatalysis
Lewisacidcatalyzedalkenedihalogenation usingseparateX+andX- sourses
acidX
X
acid
δ+δ−
H
acid Xδ− δ+
+
R2R1
R2R1X
acid
XR1
XR2
X
δ+ δ−
XX2
acid-
-
acid
18
Lewisacidcatalysis
Lewisacidcatalyzedalkenedihalogenation usingadihalogen equivalentasasinglereagent
acidX
X
acid
δ+
δ−δ−
R2R1
R2R1X
R1
XR2
X
X
X
acid X
+
acid-
-
X2
19
Lewisbasecatalysis
Lewisbasecatalyzedalkenedihalogenation usingseparateX+andX- sources
baseX
δ+ δ−
R2R1
R2R1X
R1
XR2
X
X
X
+
basebase
Xbase +
X2
base-
-
X-
20
Lewisbasecatalysis
Lewisbasecatalyzedalkenedihalogenation usingadihalogenequivalentasasinglereagent
baseX
δ+ δ−
R2R1
R2R1X
R1
XR2
X
X
X
+
base
base
Xbase +
X
XX2
base-
-X
21
PhaseTransferCatalysis
Cationicphasetransfer-catalized alkenedihalogenation
PTC
organic
aq. or solid
X3R1
R2 HR1
R2H
XX
PTC X
PTC XR1
XR2
X
+
PTC X3 M X+ M X3 PTC X+
(NR4+, PR4
+ )
Y.-M.Wang, J.Wu, C.Hoong, V.Rauniyar, F.D.Toste, J.Am.Chem.Soc. 2012, 134,12928–12931
22
PhaseTransferCatalysis
Enantioselective halocyclization via chiralanionphasetransfercatalysis
Y.-M.Wang, J.Wu,C.Hoong,V.Rauniyar, F.D.Toste, J.Am.Chem.Soc. 2012,134, 12928–12931
Me
NH
O Ph
O
N Ph
Me Br"Br+" sourse (1.3 equiv)chiral catalyst (5 mol %)
Na3PO4 (4.0 equiv)p-xylene/hex
(1:1 v/v, 0.025 M)
N NC6Me5
Br NNC6Me5
(BrF4)3
"Br+" sourse (i-Pr)3Si
(i-Pr)3Si
OO P
O
OH
i-Pr
i-Pr
i-Pr
i-Pr
i-Pri-Pr
chiral lipophilic catalyst
(precursor to chiral PT catalyst)
82%, 94% ee
23
PhaseTransferCatalysis
Enantioselective halocyclization via chiralanionphasetransfercatalysis
W.Xie, G.Jiang, H.Liu, J.Hu, X.Pan,H.Zhang, X.Wan, Y.Lai, D.Ma, Angew.Chem.Int.Ed. 2013,52,12924–12927
"Br+" sourse (1.3 equiv)chiral catalyst (10 mol %)
Na3PO4 (4.0 equiv)p-xylene/hex
(1:1 v/v, 0.025 M)
N N Br
"Br+" sourse(i-Pr)3Si
(i-Pr)3Si
OO P
O
OH
i-Pr
i-Pr
i-Pr
i-Pr
i-Pri-Pr
chiral lipophilic catalyst
quantit., 95% ee
NTs
NHCO2Me
NTs
N
Br
HCO2Me
CF3
F3C
24
PTC
organic
solid
R1R2 H
R1R2H
X
PTCR1
XR2
X
+N
N
XX
R
X
N
NR
PTC
N
NR
PTCN
N
XX
R
+
N
NR
XPTCN
NR
+
N
NR
X X X
PhaseTransferCatalysis
Anionicphasetransfer-catalyzedalkenedihalogenation
25
RR
XR H
H RX
X XC2h
C2
R
X
X
R
Cs
(homotopic termini)
(achiral)
RX
R RH H
X
X XC2v
Cs
(enantiotopic termini)
Ra b
R
X
X
R
C2
(enantiomers)
R
X
X
Ra
b
R2R1X
Cs
R1 HH R2
X
X X
C1
R1
X
X
R2
C1(constitutionallyheterotopic termini)
(enantiomers)
a b
R1
X
X
R2
a
b
R1X R1 R2
H HX
X X
C1
R1
X
X
R2
C1(constitutionallyheterotopic termini)
(enantiomers)
a b
R1
X
X
R2
a
bR2
Cs
(Enantiodetermining stepshighlightedwithboldarrows)
Symmetry-basedalkenedihalogenation via haliranium ions
chiral
achiral chiral
chiral
26
R1R2
X
R1 HH R2
a b
R1 HH R2a b
X
(racemization)
Cat*, Xfast
Cat*, X
slow
R1
XR2
X
R1
XR2
X
X
X
R1R2
X
R1 HH R2
a b
R1 HH R2a b
X
(epimerization)
fast
slow
R1
XR2
X
R1
XR2
X
Cat*, X
Cat*, X
Cat*
Cat*
X
X
Dynamickineticresolution(withsubstrate- orcatalyst-controlledhalideattackatcarbon“a”
Dynamickineticasymmetrictransformation(type1)(withsubstrate- orcatalyst-controlledhalideattackatcarbon“a”
Enantiodetermining nucleophilicattackofhalideionbykineticresolutionofhalenium ions
27
R1R2
X
R1 HH R2
a b
R1 HH R2a b
X
(racemization)
Cat*, X
attack at a
Cat*, X
attack at b
R1
XR2
X
R1
XR2
X
X
X
homomeric
Enantiodetermining nucleophilicattackofhalideion
Regiodivergent (enantioconvergent)reactionofaracemicmixture
28
Enantiodetermining haliranium ionformation
Forhaliranium ionformationtobeenantiodetermining,twoconditionsmustbemet:
1) thehalenium iontransfertotheolefinfromthe“X+”sourcemustbeirreversible
2) thehaliranium ionthusproducedmustbeconfigurationallystablepriortoitsnucleophilictrapping(itmustnotracemize).
R1 HH R2
XCat*
180 ˚
R1 HH R2
AuL*
180 ˚
R1 HH R2
OsO Cat*O
O O
Difficulttopredictstereochemical
informationvia σ∗orbital
Au(I) complexeshavelinearcoordination
geometry
Accesstoπ∗ orbitalallowstohavebetter
sterechemicalinteractionbetweenCat*andalkene
29
HH
HH
Br HHH H
free
HH
HH
Br HHH H
π-complex
HH
HH
Br
HHH H
transition state
HH
HH
Br
HHH H
π-complex
HH
HH
HHH H
free
Br
Alkene-to-alkene bromiranium iontransfer
30
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupIIIa (B,Al,Ga,In,Tl)Halides
C3H7C3H7
TiCl3•H2O (1 equiv)
CCl4, reflux C3H7C3H7
ClCl + C3H7
C3H7
ClCl
80 : 20
5% combined yield (w.r.t. TiCl3)(plus 33% of hydrochlorinated products)
anti-adduct syn-adduct
R1R2
X YH R2
R1 H
YX
π-complex
H R2R1 H
X
Xhaliranium
ion
HR2
R1 H
X
X
β-halocarbocation
or+X
-Y
X
H R2R1 H
YX
X
R1
XR2
X
-YR1
XR2
X
31
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupIVa (C,Si,Ge,Sn,Pb)Halides
OnlyPbCl4 haspowertodichlorinate alkenes.Cl
ClCl
+
quant(w.r.t. PbCl4)
no yield given
Pb(OAc)4 (1 equiv)dry HCl (excess)
DCM-40˚C to -25˚C
P.W.Henniger, E.Wapenaar, E.Havinga,Rec.Trav.Chim.1966,85, 1177–1187
R1R2
X YH R2
R1 H
YX
π-complex
H R2R1 H
X
X
haliraniumion
HR2
R1 H
X
X
β-halocarbocation
or+X
-Y
X
H R2R1 H
YX
X
R1
XR2
XR1
XR2
X
-Y
32
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupIVa (C,Si,Ge,Sn,Pb)Halides
Difluorination
AcO
Me H
Me COMe
H HAcO
Me H
Me COMe
H H
F F
Pb(OAc)4HF
DCM, -75˚C15 min
27%, (73% brsm)
R1R2
LnMX2
concertedgroup transfer
Type IVH R2R1 H
X XMLn
R1
XR2
X
-MLn
33
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVa (N,P,As,Sb,Bi)Halides
Nitrogen
ClClNCl3 (1 equiv)
0-5 ˚C
92%(w.r.t. NCl3)
J.W.Strand, P.Kovacic,Synth.Commun.1972,2, 129–137
34
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVa (N,P,As,Sb,Bi)Halides
Phosphorus
PhPh
PCl5 (2 equiv)
PhCl124 ˚C, 12h
PhPh
Cl
Cl
PhPh
Cl
Cl
+
85% 13%anti- syn-
PCl5 (1 equiv) Cl
Cl
Cl
Cl+
(2 equiv) "ionic" "radical"
With CHCl3 at 65 ˚C: 99 : 130 : 70With CCl4 at 65 ˚C:
35
MeMe
SbCl5 (1 equiv)
CCl473 ˚C, 10min
MeMe
Cl
Cl
MeMe
Cl
Cl
+
18 82:
96% combined (w.r.t. SbCl5)anti- syn-
MeMe
SbCl5 (1 equiv)
CCl476 ˚C, 10min
ClMe
Cl
Me
ClMe
Cl
Me
+
16 84:
98% combined (w.r.t. SbCl5)anti- syn-
(2.8 equiv)
(1.8 equiv)
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVa (N,P,As,Sb,Bi)Halides
Antimony
36
SbClCl
Cl
Cl
Cl
2Cl
Cl
Cl
Cl
Cl
ClSb
Cl
Cl
Sb
Cl
Cl
Cl
Cl
Cl
ClSb
Cl
Cl
ClCl
Cl
Cl
Sb
EquilibriaofSbCl5inCCl4
GroupVa (N,P,As,Sb,Bi)Halides
Antimony
R2R1
H R2R1 H
Cl ClSb
H R2R1 H
Cl
Cl5Sb Cl
SbCl5
[SbCl4]+[SbCl6]-
R1
Cl
Cl
R2
R1
Cl
Cl
R2
Cl3Sb
37
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIa (O,S,Se,Te,Po)Halides
SulfurSO2Cl2
Initiator R
SO2Cl
RCl SO2
Cl
Cl R1R2
R1R2
Cl+
R1R2
ClSO2Cl2+
-SO2
R1R2
Cl
Cl
R1R2
Cl
O SO
Cl-Cl -SO2
SO2Cl2 (1 equiv) Cl
Cl
Cl
Cl+
(1 equiv) "ionic" "radical"
At 76 ˚C: 12 : 8875 : 25At 76 ˚C with 1,3-DNB (0.2 equiv):
CCl4, 2h
79 : 21At 25-35 ˚C with SiO2 (1.8 equiv):
38
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIa (O,S,Se,Te,Po)Halides
Sulfur SO2Cl2 (1 equiv) Cl
Cl
Cl
Cl+
(1 equiv) "ionic" "radical"
At 76 ˚C: 12 : 8875 : 25At 76 ˚C with 1,3-DNB (0.2 equiv):
CCl4, 2h
79 : 21At 25-35 ˚C with SiO2 (1.8 equiv):
R1R2
X YH R2
R1 H
YX
π-complex
H R2R1 H
X
Xhaliranium
ion
HR2
R1 H
X
X
β-halocarbocation
or+X
-Y
X
H R2R1 H
YX
X
R1
XR2
X
-YR1
XR2
X
39
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIIa (F,Cl,Br,I)Halides(exceptdihalogens)
Iodine
PhICl2
Cl PhI
Clheat or hν
Ph(Cl)I
Cl R1R2+ R1
R2
Cl
R1R2
ClPhICl2+
-PhIR1
R2
Cl
Cl
Cl+
40
PhMe
PhMe
PhICl2, hν
DCM, rt
ClHPh H
Me(fast)
ClHPh Me
H
ClICl
PhClICl
Ph
PhMe
Cl
ClPh
MeCl
ClFrom trans- 92 : 8From cis- 91 : 9
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIIa (F,Cl,Br,I)halides(exceptdihalogens)
Iodine
41
R1R2
R1R2
Cl
Cl IPh
R1R2
I
Cl
PhCl
Type I -PhIR1
R2
Cl
Cl
-PhI R1R2
Cl
I ClPh
-PhI
R1R2
Cl
Cl
-PhI
Type IIinv
Type IIref
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIIa (F,Cl,Br,I)halides(exceptdihalogens)
Iodine
Possiblereactionpathwaysfortheionicdichlorination ofalkeneswithPhICl2
42
HF
F
F
IMe δ+
δ−
R1R2
- HF R1R2
ITol
F
F
R1I
F
F 4-Tol
R2F
- 4-Tol- F-
R1
F
R2
F
MeO2C MeO2C
4-TolIF2 (1.3 equiv)
DCM/Et3•5HF (1/1 v/v)0˚C, 3h
55%
Alkenedihalogenation withmaingrouphalidesasreagentorcatalysts
GroupVIIa (F,Cl,Br,I)halides(exceptdihalogens)
Difluorination
43
MeMe
MoCl5 (1 equiv)
CCl474 ˚C, 20min
MeMe
Cl
Cl
MeMe
Cl
Cl
+
8 92:
85% combined (w.r.t. MoCl5)anti- syn-
MeMe
MoCl5 (1 equiv)
CCl474 ˚C, 20min
ClMe
Cl
Me
ClMe
Cl
Me
+
15 85:
92% combined (w.r.t. MoCl5)anti- syn-
(35 equiv)
(25 equiv)
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
GroupVI(Cr,Mo,W,)metalhalides
Molybdenum
44
R2R1
H R2R1 H
Cl ClMo
H R2R1 H
Cl
Cl5Mo Cl
MoCl5
[MoCl4]+[MoCl6]-
R1
Cl
Cl
R2
R1
Cl
Cl
R2
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
GroupVI(Cr,Mo,W,)metalhalides
Mechanismfortheformationofsyn- andanti-dichlorination products
45
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
GroupVII(Mn,Tc,Re,)metalhalides
Manganese(VII)
C4H9C4H9
C4H9C4H9
C4H9
ClC4H9
Cl
C4H9
ClC4H9
Cl
KMnO4 (1 equiv)BnNEt3Cl (1 equiv)Me3SiCl (4 equiv)
DCM, 0˚C to 20˚C
KMnO4 (1 equiv)BnNEt3Cl (1 equiv)Me3SiCl (4 equiv)
DCM, 0˚C to 20˚C
94%
81%
R1R2
Cl [Mn]H
Cl
R1 HR2
[Mn]H
Cl
R1 HR2
[Mn]
Cl
-[Mn]
Cl
R2HCl
R1H
46
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
GroupVII(Mn,Tc,Re,)metalhalides
Manganese(III)and(IV)
C3H7Me
C3H7
ClMe
Cl
KMnO4 (1 equiv)BnNEt3Cl (1 equiv)Me3SiCl (4 equiv)
DCM, 0˚C to 20˚C
95%, 64:36 dr
R1R2
Cl MnIII MnII
R1
ClR2
Cl MnIII MnII
R1
ClR2
Cl
MnO2 (1.5 equiv)Me3SiCl (6 equiv)
THF, 40˚C to 60˚C+Cl
Cl
ClCl
85% 8%
R1R2 Cl MnIV
R1
ClR2 R1
ClR2
Cl
Cl
Cl MnIII
-MnII
47
R1R2
[PdII] ClR1
R2
Cl
[PdII]
R1R2
Cl
[PdII]
or
syn anti
Known
R1 R2
[PdII] "Cl+" or "Cl-" + [O]
R1 R2
[PdII]
R1 R2
[PdII]or
Unknown
R1R2
[PdII] Cl
"Cl+" or "Cl-" + [O]R1
R2
Cl
ClR1
R2
Cl
Clor
syn anti
retentive invertive
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
Group10(Ni,Pd,Pt,)metalhalides
Palladium
48
BuPdCl2(PhCN)2 Bu
[PdII]
p-benzoquinoneLiCl, AcOH,rt Bu
ClCl
(no yield or dr published)
Alkenedihalogenation withtransitionmetalhalidesasreagentorcatalysts
HO OH Pd(II)
[PdII]
X-, PBQ
[PdII]O
O
O
O
Pd0
Y-
XY
2H+
J.-E.Bäckvall, C.Jonasson,TetrahedronLett. 1997,38, 291–294
BuPd(OAc)2
p-benzoquinoneLiBr, AcOH,rt
BuBr
Br
(58%)
49
Thankyouforyourattention!
50
R1R2
X YH R2
R1 H
YX
π-complex
H R2R1 H
X
Xhaliranium
ion
HR2
R1 H
X
X
β-halocarbocation
or+X
-Y
X
H R2R1 H
YX
X
R1
XR2
X
-YR1
XR2
X
51
R1R2
LnMX2
anti-addition of M-X
H R2R1 H
M
π-complex
LnX
X
H R2R1 H
M
X
X Ln
-iranium ion
or M
XHR2
R1
HX
Ln
R1 HH R2X
X MLn
anchimericallyassisted
XH
R1H
R2MX
Ln
concerted
or R1
XR2
XType IIret
(retentive C-Xbond formation)
Type IIinv(invertive C-X
bond formation)
M
XHR2
R1
HX
Ln
X
R1
XR2
X
-MLn
SN2
-MLn
52
R1R2
LnMX2
syn-addition of M-X
H R2R1 H
4−membered transition state
MH
R1
XLn
H HR1 R2
X
X MLn
anchimericallyassisted
R1H
MX
Ln
concerted
or R1
XR2
XType IIIret
(retentive C-Xbond formation)
Type IIIinv(invertive C-X
bond formation)
M XH R2R1 H
XLn
X
R1
XR2
X
-MLn
SN2
M XXLn X
HR2
X
R2H
-MLn
53
R1R2
LnMX2
concertedgroup transfer
Type IVH R2R1 H
X XMLn
R1
XR2
X
-MLn
R1R2
"X "
X atom transferType V
R1R2
X
β-halo radical
R1R2
X
X Y
X Y -YR1
R2
X
X
chain reaction if Y•=X• or Y•→X• + Yʹ
RadicalTypeV