344. The reactions of hydrazones and related compounds with strong bases. Part I. A modified Wolff–Kishner procedure

Abstract

A new Wolff-Kishner procedure, involving potassium t-butoxide in toluene, has been used to reduce benzophenone and also two compounds [cholest-4-en-3-one and the a-amino-ketone (I)] that give abnormal products under conventional conditions. THE Wolff-Kishner reaction of hydrazones and semicarbazones is a popular method for reducing aldehydes and ketones to hydrocarbons, but there are numerous reports of the formation of unexpected products. For example, reduction of the carbonyl groups of ap-unsaturated aldehydes and ketones is frequently accompanied by a shift in the position of the double bond.1 In the Wolff-Kishner reaction of many a-amino-ketones and related compounds, an elimination competes with the normal reduction, and in some instances is the predominant reacti0n.~*3 Typical procedures for the Wolff-Kishner reaction involve the use of metal alkoxicles at 180-220" or the use of potassium hydroxide in ethylene glycol at ZOO", and these rather vigorous conditions may be responsible for some of the anomalous reactions. The Wolff-Kishner reaction is usually considered 334 to occur by the following mechanism : B-./-? 0 H6 \ ,c=N-NH, >c-N=NH >CH-N=N-N, + >CH-.r_t >CH,

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

“…Reactions from the benzophenone hydrazone to the diphenylmethane in aprotic solvents such DMSO [10] and toluene [11] are discussed. Even if proton sources are absent, paths similar to VIII ph (hydrazone) → IX Ph ( TS4 ) → X Ph → XI Ph ( TS5 ) → XII Ph (diimine) → XIII Ph ( TS6 ) → XIV Ph (carbanion) may be taken.…”

“…Cram et al obtained diphenylmethane H 2 C(Ph) 2 in 85% yield from benzophenone hydrazone Ph 2 C=N–NH 2 and potassium tert -butoxide KO t -Bu in DMSO [10]. Grundon et al obtained the product also in 85% yield in toluene [11]. These non-aqueous experimental results indicate that the tert -butoxide ion directly participates in the proton shifts.…”

Catalytic Generation of Carbanions through Carbonyl Umpolung

“…In ar egular WK process,t he reaction proceeds through the formation of hydrazones from ac arbonyl compound and hydrazine.Asubsequent deprotonation-tautomerization sequence occurs to give the diazene intermediate from the hydrazone.A fter as econd deprotonation, this intermediate rapidly loses molecular nitrogen to give the carbanion, which is then protonated to yield the alkane product (Scheme 2A). [6a] Thef ormation of the two key intermediatesah ydrazone and the diazene anion-can considerably influence the course of aW Kp rocess.M any elegant modifications,i ncluding the well-known Huang-Minlong, [12] Barton, [13] Cram, [14] and Henbest [15] procedures,have focused on amore efficient formation of the hydrazone by removal of water from the reaction medium, whereas Caglioti [16] and Meyers [17] have utilized substituted hydrazones as alternatives to the classical WK reaction, thereby allowing the facile generation of the diazene intermediate.Inparticular,the use of sulfonyl hydrazone in the Caglioti modification not only allows the WK reduction to occur under mild conditions but also inspired the generation of substituted carbanions by reacting sulfonyl hydrazone with organometallic reagents (e.g. RLi, RMgBr;S cheme 2B).…”

Carbonium ion rearrangements in the deltacyclane ring system. IV. Solvolytic reactions of exo-7-isodeltacyclyl brosylate

“…Short-path distillation of the product, bp 45-50°(0.2 mm), gave 19.1 g (0.10 mol, 50% yield) of clear, colorless product. The nmr spectrum has absorptions at r 6.05 and 5.42 (t, J = 2.2 and 3.5 Hz, respectively), which are assigned to endo CHC1 and exo CHC1, in a ratio of 90:10: ir (90:10 mixture, neat) 3086 (olefinic C-H stretching), 1786 (carbonyl stretching), 1333, 1015, 741, 691 cm-1; nmr (90:10 mixture, 60 MHz, CCU) r 8.26 (doublet of triplets, 1 H, J = 10, 3 Hz, methylene proton), 7.95 (d, 1 H, J = 10 Hz, methylene proton), 6.95 (broad singlet, 1 H), 6.53 (m, 2 H, bridgehead protons), 6.05 (t, 1 H, J = 2.2 Hz, -CHC1), 3.83 (m, 2 H, olefinic protons).…”