THP ether protective group

Tetrahydrohydropyranyl (THP) ether
is not a leaving group. stable under basic conditions.
can't eliminate even bata to Grigyard anion.

Formation:
catalytic amount of con. HCl + alcohol + 3,4-dihydro-2H-pyran
no solvent. 0 C to rt. overnight.
CeCl3-7H2O 5%, NaI 5%, no solvent. 1-10hr. a new way to make the thp ether.

deprotection:
1. TsOH in EtOH/MeOH.

sacrificing ester

The idea of sacrificing ester.
NaH or KH usually contains some NaOH/KOH which will hydrolyze esters.
Trace of water can also react with KH/NaH to form NaOH/KOH.

a non enoliazable ester can be used to remove the metal hydroxide.
methylbenzoate works fine.

convertion of 3,4-alkene ester to conjugated ester

Base: DBU or NaH
solvent: Et2O or toluene or MeCN
rt. long reaction time.


methyl benzoate can be used as sacrificed ester to prevent the ester from hydrolysis.

Bromination on aromatic ring

o-Bromination of phenol.
: iPr-NH, slow addition of 1 eq. of NBS in DCM at 0 C.

optical rotation calculation

d: sodium line.
temperature: Celsius.
1. a neat = a/densiy

2. for a solution:
a = 100a/c (c= xx g/100ml)
ex: a 20 d = +6.2 (c 1.2, EtOH)