THE PREPARATION OF 3-(2-PHENYLETHENYL)-1H-PYRAZOLES FROM DILITHIATED (3E)-4-PHENYL-3-BUTEN-2-ONE HYDRAZONES

Preparation of 2‐(1H‐pyrazol‐5‐yl)benzenesulfonamides from polylithiated C(α),N‐carbo‐tert‐butoxyhydrazones and methyl 2‐(aminosulfonyl)benzoate

“…7, 127.4, 128.1, 128.5, 129.2, 129.4, 130.6, 132.4, 133.5, 142.0 and 151.4 3,125.3,127.5,128.1,128.6,128.8,129.2,131.5,132.1,132.2,141.1,143.0,and 150.7. LCMS,mw,299.4 6,124.0,126.5,126.8,127.9,127.8,128.1,128.3,128.7,132.1,132.2,132.7,133.1,and 141.3. LCMS,mw,349.4 4.14;N,11.82.…”

“…One of our synthetic interests and endeavors has been the condensation-cyclization of polylithiated C( ),N-hydrazones with aromatic esters and related reagents [4][5][6] for the preparation of pyrazoles. A part of our developing studies has been the condensation of these 1,4-dilithiated hydrazone intermediates with routine or challenging anionic electrophilic reagents such as lithiated ethyl benzoylacetate (dilithiated phenylhydrazones give phenacylpyrazoles) [7], lithiated methyl salicylates (dilithiated carboalkoxyhydrazones give pyrazolobenzoxazinones) [8], or lithiated ethyl oxanilate (dilithiated phenylhydrazones gives pyrazolecarboxamides) [9].…”

Styrylpyrazoles: Properties, Synthesis and Transformations

“…Then, compounds 37 were deprotonated with an excess of lithium diisopropylamide (LDA), and the resulting dilithiated intermediates 38 were condensed at the carbanion center with a variety of substituted benzoate esters, such as methyl benzoate, methyl 4-t-butylbenzoate, (lithiated) methyl 4-hydroxybenzoate, or methyl 3,4,5-trimethoxybenzoate affording 39. After acid cyclization of 39 with 3 N hydrochloric acid, the 3-styrylpyrazoles 40 were isolated (Scheme 7)[69]. Reaction of benzalacetone 36 with hydrazines to produce hydrazones 37 and their transformation into (E)-3-styrylpyrazoles 40[69].Scheme Reaction of oxoketene dithioacetals 33 with hydrazine hydrate to synthesize (E)-3(5)-styrylpyrazoles 34[68].In 2001, Pastine et al reported the synthesis of (E)-3-styrylpyrazoles starting from benzalacetone 36, which was converted into the corresponding hydrazones 37 by reaction with hydrazine derivatives.…”

“…After acid cyclization of 39 with 3 N hydrochloric acid, the 3-styrylpyrazoles 40 were isolated (Scheme 7)[69]. Reaction of benzalacetone 36 with hydrazines to produce hydrazones 37 and their transformation into (E)-3-styrylpyrazoles 40[69].Scheme Reaction of oxoketene dithioacetals 33 with hydrazine hydrate to synthesize (E)-3(5)-styrylpyrazoles 34[68].In 2001, Pastine et al reported the synthesis of (E)-3-styrylpyrazoles starting from benzalacetone 36, which was converted into the corresponding hydrazones 37 by reaction with hydrazine derivatives. Then, compounds 37 were deprotonated with an excess of lithium diisopropylamide (LDA), and the resulting dilithiated intermediates 38 were condensed at the carbanion center with a variety of substituted benzoate esters, such as methyl benzoate, methyl 4-t-butylbenzoate, (lithiated) methyl 4-hydroxybenzoate, or methyl 3,4,5-trimethoxybenzoate affording 39.…”

Preparation of 2-(1-phenyl-1H-pyrazol-5-yl)benzenesulfonamides from polylithiated C(α),N-phenylhydrazones and methyl 2-(aminosulfonyl)benzoate

“…Our current synthetic emphasis has been on the condensationcyclization of polylithiated C(α),N-hydrazones, such as acetophenone phenylhydrazone, with aromatic esters and related reagents [19][20][21]. A part of this developing study has been the condensation of these 1,4-dilithiated intermediates with challenging anionic electrophilic reagents, such as lithiated ethyl benzoylacetate [22], lithiated methyl salicylates [23], or lithiated ethyl oxanilate [24].…”