A Novel Synthesis of 1,5-Diphenylpyrazolone-3¹

Base catalysed rearrangements involving ylide intermediates. Part 16. The preparation and thermal rearrangement of allylammonioamidates

“…In contrast with earlier reports:*'o in all cases both reaction products could be isolated. This qualitative investigation suggested that the rates of [1,2] and [3,2] rearrangement depended upon the substituent X (see 11) in a different manner and the cinnamylammonioamidates were investigated in more detail. The rates of the competing [1,2] and [3,2] rearrangements of these ylides (lla), (llb), (lld), and (llg) are reported in Table 2, and it can be seen that both reactions are sensitive to changes in the group X.…”

“…

The ammonioamidates (7) and ( 11) undergo [1,2] rearrangement (R3 = CH,Ph) and competing [1,2] and [3,2] rearrangements (R3 = allyl). The rates of the [1,2] and [3,2] rearrangements of the cinnamyl ammonioamidates (1 1 a), (1 1 b), (1 1 d), and (1 1 g) show similar dependence on the nature of the substituent X.

…”

“…

The ammonioamidates (7) and ( 11) undergo [1,2] rearrangement (R3 = CH,Ph) and competing [1,2] and [3,2] rearrangements (R3 = allyl). The rates of the [1,2] and [3,2] rearrangements of the cinnamyl ammonioamidates (1 1 a), (1 1 b), (1 1 d), and (1 1 g) show similar dependence on the nature of the substituent X. The rate of the [1,3] rearrangement of the reaction products (14b), (14d), and (14g) is relatively insensitive to substituent effects, suggesting that the rates of ammonioamidate rearrangements are largely controlled by conjugation between the group X and the NCO system.

…”

“…The ammonioamidates (1 ; X = COR) are the best known compounds of this type and their structure, as represented by the mesomeric system (2), is closely analogous to that of the acyl-stabilised ammonium ylides (3) which have been discussed in earlier parts in this ~e r i e s . ~ It was, therefore, of interest to study the sigmatropic rearrangements of ammonioamidates (2) in which the group R2 might participate in [1,2] (R2 = benzyl) and [3,2] (R2 = allyl) rearrangements.…”

“…The products (9e) and (9f) were, as expected, converted totally by [1,3] rearrangement into (9c) and (9d) when heated Table 1. Competing [3,2] and [1,2] In (9): e, R' and R2 = H and Me, R3 = CHPhCH=CH2; f, R' = H, R2 = Me, R3 = CMe2CH=CH2 at 138 "C. These results appeared to be in conflict with the earlier w ~r k , ~* ' ~ but the oxopyrazolidinium system (7) is restricted to a transoid arrangement of the -O-CcN-N+ grouping whereas acyclic ammonium ylides are known to adopt a cisoid arrangement of the analogous -0-CZC-N' g r 0 ~p i n g . l ~…”