Novel formation of 6-acyl-5-(2-pyrrolyl)-3 H -pyrrolizines by base-catalysed condensation of pyrrole-2-aldehyde with methyl ketones

Synthesis and NMR Studies of (E)-1-Aryl-3-(2-pyrrolyl)-2-propenones and (E)-3-Aryl-1-(2-pyrrolyl)-2-propenones

“…Although many of the products were soluble in CDCl 3 , some were not soluble enough to make 0.1 M solution. Therefore, DMSO-d 6 Although the splitting patterns for the 3-, 4-, and 5-Hs in 3 and 6 are similar, the order of appearance of them from the up field is different: 4-H < 3-H < 5-H for 3 and 4-H < 5-H < 3-H for 6. It is notable that the effect of the carbonyl group in 6 on the chemical shift of the 3-H of the pyrrole ring is far greater (Δδ = 1.37) than those of the typical carbonyl derivatives of pyrrole reported in the literature: Δδ = 0.93 for CHO; 0.78 for COCH 3 ; and 0.79 for COOCH 3 .…”

“…3 On the other hand, an aldol condensation of 1 with methyl ketones was reported. [4][5][6][7] However, the reaction seems not to be straightforward as the stoichiometric equation indicates. An early study reports a reaction time of four weeks with a mixture of 1 (0.9 g), acetophenone (2k, 3 mL), and 1 M-KOH solution (3 mL) to give 3k (no yield given).…”

“…When an 1:2 mixture of 1 and 2k in ethanolic KOH (20%) was allowed at room temperature for 4 days, a mixture of 3k and 9 was formed in 29% and 29%, respectively. 6 On the other hand, a solution of 1 (5.26 mmol) and 2k (5.26 mmol) in ethanol (2.1 mL) was mixed with 10% NaOH solution (0.5 mL) and stirred overnight at room temperature to give 3k in 48.5% yield.…”

6-(2-Hydroxybenzoyl)-5-(pyrrol-2-yl)-3H-pyrrolizine

“…It has also been found that basecatalyzed 1:2 condensations between 2-hydroxyacetophenones and p-nitrobenzaldehyde in aqueous methanol gave trans-2,3-dimethoxy-3-(p-formylphenylamino)-4 H -nitro¯avanones as interesting novel products (Mallik et al, 1992). This encouraged us to study similar 1:2 condensations between phenyl methyl ketones and pyrrole-2-carbaldehyde, from which we obtained mixtures containing the usual (E)-1-acyl-3-(pyrrol-2-yl)-2-propen-1-ones but also 6-acyl-5-(pyrrol-2-yl)-3H-pyrrolizines as unexpected novel products (Mallik et al, 2002). Pyrrolizines and their derivatives are of considerable interest in view of both their occurrence as natural products and their potential biological activities.…”

A novel synthesis of stable 3H-pyrrolizine fused diazaborepin

“…3H-pyrrolizine 1 24-26 consisted of bicyclic 5-5 systems with one nitrogen atom at the ring junction was obtained under organocatalyst with comparable yield and shorter time compared to previous base conditions. 23 Utilizing B-N chemistry, B-C bonds in classical borepin core was replaced by B-N bonds in a novel borepin core, diazaborepin such as diazaphosphepines reported by Loo and co-workers. 22 The route developed is shown in Scheme 1 and relies on an organocatalyst (piperidinium acetate) which formed from the reaction of piperidine and glacial acetic acid in situ and had been used in Knoevenagel reaction extensively.…”