Level 2 - Case 30
Diels-Aider Reactions of N-Acyl-1 ,2,4,5-tetrazines
Key point: Inverse electron demand Diels-Aider reaction
Diels-Aider Reactions of N-Acyl-1,2,4,5-tetrazines
The reactîon between N-acyl-6-amîno-3-(methylthîo)-1,2,4,5-tetrazînes 1 wîth
electron-rich dienophiles 2 gives the corresponding 1,2-diazines 3 in excellent
yields and with high regioselectivity (Scheme 30.1 ).
NHR 1
N~N
11
1
Nif'N
SCH3
1
1a, R 1 =Ac
2
+ JL
R
2
EDG
2
1 b, R 1 = BOC; R 2 = H, OMe, alkyl
A
N~:R1
11
N f i R2
SCH3
3
EDG = electron-donating group: OEt, OMe, OTs, pyrrolidino, morpholino
Scheme30.1
Consîderîng that the dîenophile employed în the reaction îs ethyl vînyl ether,
answer the fâllorving questions:
1. Propose a reasonahle mechanism to interpret how diazines 3 areformed.
2. Predict rvhich tetrazine would be more reactive towards this dienophile.
3. Drav.· the structure of the reaction products between tetrazines 1 and ethyl vinyl
ether.