A Direct Synthesis of 2-(Trimethylstannyl)pyrroles from Michael Acceptors and Stannylated Tosylmethyl Isocyanide¹

Abstract

A series of 2-(trimethylstannyl)pyrroles 3, with substituents at the 3- and 4-positions, is synthesized efficiently by a base-induced reaction of stannylated TosMIC with Michael acceptors. Stille cross-couplings with bromobenzene and double cross-couplings with 1,4-dibromobenzene have been achieved successfully with the N-methyl derivative (5a) and the N-Boc derivative (6a) of 3-benzoyl-2-(trimethylstannyl)-4-phenylpyrrole (3a), despite the bulk of these stannylpyrroles. Homo-coupling reactions of the same stannylpyrroles with the corresponding bromopyrroles (prepared from stannylpyrroles 3 and NBS) were unsuccessful, probably for steric reasons.

Synthesis of aromatic heterocycles

“…88 By prior reaction with base and chlorotrimethylstannane, its addition to enones provided a direct route to 2-trimethylstannylpyrroles. 89 This provides the basis for the preparation of other 2-substituted pyrroles. In a similar way, 3,4-bis(trimethylsilyl)pyrrole can be used as a precursor of other β-substituted pyrroles; this has been prepared efficiently by 1,3-dipolar cycloaddition of the azomethine ylide derived from the aziridine 57 to bis(trimethylsilyl)acetylene.…”

Practical one-pot sequential procedure for the preparation of N-arylated 3,4-disubstituted pyrroles from alkenes

“…As shown in Table 2, all acrylate derivatives (2a-d) gave the corresponding N-arylpyrroles 1a-d in satisfactory yields (entries 1-4). However, when chalcone (2e) was used as a substrate, the intermediate 4-phenyl-3-benzoylpyrrole (3e) [34] was isolated instead of the expected N-arylated product 1,4-diphenyl-3-benzoylpyrrole (1e). The control experiments proved that this problem was caused by the fact that 3e had a very bad solubility in toluene.…”

p -Toluenesulfonylmethyl Isocyanide: a Versatile Synthon in Organic Chemistry

“…Using R as 4-MeOC 6 H 5 and R 1 as NO 2 in 160, the reaction with TosMIC in the presence of DBU leads to formation of the pyrrole 162, the NO 2 group being the leaving group (Scheme 63) [62]. The proposed mechanism for the formation of 165 is outlined in Scheme 66 [64]. The introduction of a substituent at the 3-position of pyrrole is significant as these intermediates are used for the synthesis of natural products and conducting polymers.…”