Anionic 3 + 2 Cycloaddition

Abstract

7 6 5 4 3 2 1 (3) ( 3 ) ( 4 ) ( 4 ) 14) Figure. ' H -N M R spectrum of bis(dipivaloylmethyl)rnercury(rI) ( 4 ) in CDCI, at -40°C. a: HC (ketone); b: HC (enol); c: (H,C),C (ketone); d: (H,C),C (enol). Styrene 20 [b] 2,2,3-Triphen-85 86-87 ylpyrrolidine Tolan 20 [bl 2,2,3,4-Tetra-43 138-139 phenylpyrroline ylpyrrolidine Styrene 0 2,3,5-Triphen-75 68 frans-0 2,3,4,5-Tetra-39 110-1 1 1 Stilbene phenylpyrrolidine Tolan 40 [cl 2,3,4,5-Tetra-73 215-2171dl phenylpyrrole reaction of the $-diketones (7) and (8) with bis(hexamethy1-disi1ylamido)mercury ( 9 ) 18991 in dry ether. In this manner it was possible t o prepare for the first time the sparingly soluble compound (5) in analytically pure form. The methods given in the literature[los '11 always lead t o products which contain OH, acetate, or C1 as ligands, and which are ca. 3 % deficient in carbon, and exhibit several intense bands in the C=O region of the IR spectrum[121. Since pure (S), like ( 4 ) (in KBr), shows only one sharp C=O band at 1678 cm-1, the metal in mercury(rr) acetylacetonate (5) must also be bonded t o the central C atom. Bis(diucefylmethyl)inercury(rlJ (5)A solution of acetylacetone (8) (12.02 g) in ether (SO ml) is added with stirring t o a solution of ( 9 ) (3.24 g) in absolute ether (30 ml). A finely crystalline, colorless precipitate is formed immediately, yield 2.51 g (100 %). After recrystallization from acetylacetone, compound (5) decomposes at temperatures above 254 "C. The compound is very sparingly soluble in all common solvents. Bis(dipivaloylmethyl)mercury(~~) (4) has been prepared inthe same way; yield 91 %, m.p. 1 9 S 1 9 7 ' C (dec.). Its IR spectrum can be superimposed o n that of the compound prepared from (7) and mercury(rr) acetate according t o the method given in ref. 161,

Aroylation of carbanions derived from N-(diphenylmethyl)arylmethanimines. A synthesis of 4-aroyloxy-2-azabuta-1,3-dienes

“…phenyl-2-azabuta-1,3-diene (4b): 3.548, 73% as yellow crystals; m.p. 178-180 "C; 6,3.76 (3 H, s, MeO), 3.83 ( 1273, 420 (22), 419 (66), 404 (21), 403 (64), 373 (20), 166 (21), 165 (56) 268 (E 37630) and 384 (9756) nm; m/z 584 ( l % ) , 449 (18), 434 (26), 433 (loo), 166 (6), 165 (17)…”

Base‐Mediated Generation of Ketenimines from Ynamides: [3+2] Annulation with Azaallyl Anions

“…11,12 Overall, reports of 1,3 dipolar cycloaddition with a ketenimine as the dipolarophile remain rather scarce. [13][14][15] Moreover, [3+2] cycloadditions with non-or semi-stabilized azallylanions 16,17 were mostly developed with olefins as the dipolarophiles. [18][19][20] This serendipitous discovery thus gave us the opportunity to explore some unprecedented annulation reactions towards nitrogen-rich heterocycles.…”

Palladium‐Catalysed Decarboxylative Generation and Regiodivergent Prenylation of 2‐Azaallyl Anions

“…Interestingly, increasing the catalyst loading resulted in a decrease in yield for 3a (79%) with a concomitant increase in the amount of inseparable [3+2] cyclo-adducts between the 2-azaallyl anion intermediate and the dibenzylidenacetone (dba) ligand derived from the palladium pre-catalyst (entry 4). [14] Switching the source of palladium to [Pd(allyl)Cl] 2 in DMSO showed only poor conversion exclusively to the linear regioisomer 4a (entry 5), but using the ligand 1,2bis(diphenylphosphino)ethane (dppe) resulted in complete conversion of imino ester 1a to a mixture of prenylated regioisomers favouring the linear product 4a (1:3.6, entry 6). As anticipated from the highthroughput screens, increasing the temperature to 130 °C resulted in formation of linear isomer 4a as the sole DcPn product (91%, entry 7).…”