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Chem 112A Summary of Alkene Reactions - READ NOTES AT BOTTOM!)
Starting with a generalized alkene: C C
HX
ether X = Cl, Br, I General Product Selectivity Intermediate / TS C C
H X
regioselective (Markovnikov) cation X 2 CH 2 Cl 2
C C
X
X
stereoselective (anti additon - trans dihalide) halonium X 2 , H 2 O CH 2 Cl 2
C C
X
OH
stereoselective (a nti additon - trans halohydrin); regioselective halonium (also via NBS/ H 2 O / DMSO; DMSO provides O in hydroxyl) H 3 O+ C C
H OH
regioselective (Markovnikov) cation (" H 3 O+^ " is a generalized way to indicate the use of aqueous acid; common acids are HX, H 2 SO 4 , or H 3 PO 4 ) heat (!)
- Hg(OAc) 2 , THF, H 2 O C C
H OH
regioselective (Markovnikov) mercurinium
- NaBH 4
- BH 3 - THF C C
H OH
regioselective (anto-Markovnikov); stereoselective ( syn addition of H and OH to alkene) 4-centered transition state
- NaOH, H 2 O 2 , H 2 O NOTES: -the products shown are generalized products and do not imply stereo- or regiochemistry. Be sure you know how to depict products showing such selectivities! (see problem set) -unless ottherwise specified (e.g. BH 3 ), other solvents may be used -if we covered them in class, know the appropriate mechanisms THF or ether required with BH 3 halide 1,2-dihalide halohydrin alcohol
Chem 112A Summary of Alkene Reactions - continued
C C
H 2
PtO 2 or Pd/C ROH or CH 3 COOH
C C
H H
stereoselective (syn addition - cis addition product) transfer of 2 H on catalyst surface - both add to same alkane "face" of pi bond possible solvents Starting with a generalized alkene: General Product Selectivity Intermediate / TS mCPBA CH 2 Cl 2
C C
epoxide O (^) stereoselective (syn addition - cis addition product) one-step concerted reaction (also via halohydrin and KOH or NaOH, H 2 O) C C cyclopropane Cl Cl CHCl 3 KOH also via CH 2 I 2 , Zn(Cu), ether - cyclopropane w/o 2 Cl (Simmonds-Smith)
- OsO 4 , pyridine; 2) NaHSO 3 , H 2 O or
- OsO 4 , acetone, H 2 O; 2) NMO or KMnO 4 , NaOH, 0oC (must be cold & basic)
C C
HO OH
1,2 cis diol stereoselective (syn addition - cis addition product) cyclic osmate intermediate (or manganate) also, cleave epoxide with NaOH or KOH, H2O to yield 1,2 trans diol Cleavage Reactions from Alkene and 1,2 Diol:
- O 3
- Zn, H 3 O+
C C
R
R
H
R'
C O
R
R
O C
H
R'
- (2 products) KMnO 4 H 3 O+^
C O
R
R
O C
OH
R'
- (2 products) note the difference! C C
HO OH HIO 4
H 2 O, THF
C
C O
R
R
O C
H
R'
Cyclopropane from Alkene: carbene cyclic ozonide cyclic periodate stereoselective (syn addition)
