Table 6. Thermal rearrangement of isolated VCP.
Entry | VCP precursor |
Temp. (°C) | VCPR product |
||||||
# | X | R1 | R2 | R3 | # | Conv. a (%) | Yield b (%) | ||
1 | 19a | F | Ph | CON(Me)OMe | H | 95 | 35 | 100 | 97 |
2 | 19b | F | Ph | H | CON(Me)OMe | 160 | 0 c | — d | |
3 | 20a | F | Ph | CO2Et | Me | 155 | 36 | 0 c | — e |
4 | 21a/b f | F | Ph | H/CN | H/CN | 90 | 37 | 71 g | — |
5 h | 21b | F | Ph | H | CN | 160 | 100 | 48 i | |
6 | 47 | H | Ph | CO2Et | H | 220 | 38 | 100 | 40 j |
7 | 19a | F | Piperonyl | CO2Et | H | 70 | 39 | 42 k | 18 l |
a Conversion to product (determined by 1H or 19F NMR).
b Isolated yields unless otherwise stated.
c Full conversion of VCP precursor was observed.
d Decomposition was observed.
e Clean product could not be isolated from crude reaction mixture.
f 3 : 2 mixture of 21a and 21b, respectively.
g Crude mixture also contains 26% 21b and 3% cis-42 (determined by 19F NMR).
h Using crude reaction mixture from entry 4.
i 6 : 1 ratio of difluorocyclopentene 37 and alkene isomer 43 (by 1H NMR).
j 22% of cis-cyclopentene 38b was also isolated.
k Crude reaction mixture also contains 58% of [3,3]-product (44, by 19F NMR).
l 11% of 44 was also isolated.