Question

Which of the following reagent will react with pyrrole to form 2 formyl pyrrole?

Answer 1

O-Ethyl 2-thionoester pyrrole 1a, initially prepared via treatment of the corresponding 2-carboxylate pyrrole with Lawesson's reagent,9 was reacted with excess 2800 RANEY® nickel to provide the 2-formyl pyrrole 2a in 67% isolated yield (Table 1, entry 1).

Answer 2

• The reagent which will react with pyrrole to form 2 formyl pyrrole is 2800 RANEY® nickel.

• O-ethyl 2-thionoester pyrrole 1a was synthesised by reacting excess 2800 RANEY® nickel with the appropriate 2-carboxylate pyrrole using Lawesson's reagent9, yielding the 2-formyl pyrrole 2a in a 67 percent isolated yield.

Explanation:

• 2-Functionalized pyrroles have a lot of applications in synthetics. The synthesis and reactivity of 2-thionoester (–C(S)OR) pyrroles are:-
• From aliphatic starting materials, 2-thionoester pyrroles were produced utilising a Knorr-type method.
• Using RANEY® nickel, 2-thionoester pyrroles were reduced to the correlating 2-formyl pyrroles, or the deuterated formyl variant, in one step, eliminating the need for the hydrolysis/decarboxylation/formylation steps that are usually necessary to convert Knorr-type 2-carboxylate pyrroles to 2-formyl pyrroles.
• 2-Thionoester pyrroles were shown to be resistant to the functional group interconversions that have become common in their parent 2-carboxylate pyrroles.