Alkenes from Tosylhydrazones

Abstract

In 1952, Bamford and Stevens observed that tosylhydrazones of aliphatic ketones yielded alkenes when treated with the sodium salt of ethylene glycol in boiling ethylene glycol. In addition to the alkene, molecular nitrogen, and p‐toluenesulfinate anion were produced. This chapter reviews such syntheses of alkenes from tosylhydrazones and the formation of cyclopropanes and acetylenes from tosylhydrazones because the several reactions involved are so closely interrelated. The four major reaction types are reviewed here: (1) base‐induced decomposition of tosylhydrazones in protic solvents and (2) in aprotic solvents (3) reactions of tosylhydrazones with alkyllithium reagents and (4) fragmentation reactions of alpha, beta‐epoxytosylhydrazones and analogous systems. Reactions 1 and 2 are called the protic and aprotic Bamford‐Stevens reaction.

Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

“…The thermal decomposition of tosylhydrazones also yields carbenes; see for instance, the Bamford-Stevens reaction. 3 Even more ubiquitous is the use of N-heterocyclic carbenes (NHC) as ligands in organometallic systems [4][5][6][7][8][9][10] or as organocatalysts. [11][12][13][14][15] Here we examine a strained cycloalkylcarbene: cyclobutylidene.…”

The Importance of the 5-Alkyl Substituent for the Violet Smell of Ionones: Synthesis of Racemic 5-Demethyl-α-ionone

“…With compound 15 in hand, at first we attempted its direct conversion to olefin 14 through a Shapiro-like reduction of the carbonyl group [19]. The product 14 was indeed formed, however, in <20% yield, likely due to the retro-aldol-like decomposition of the p-toluensulfonylhydrazone 22 of ketone 15, upon treatment with excess LDA, in accordance with the mechanism shown in Figure 5.…”

“…Indeed, already in 1941, Jitkow and Bogert affirmed that the violet smell of ionones critically depends on the presence of three methyl groups attached to a cyclohexene nucleus, two of which should be adjacent to the enone side-chain [18] In this paper we describe a concise synthesis of enone 12 and its odor evaluation. At the beginning, our planned synthetic strategy ( Figure 3) was based on the preparation of the key cyclohexenylcarbinol intermediate 14, in principle obtainable through the Shapiro reaction [19] of ketone 15. This precursor was envisoned to derive from the product of a Lewis acid-catalysed cyclization of ketoester 16, which could readily be assembled from commercially available compounds 17 and 18.…”

Bent Singlet Cyclobutylcarbene: Computed Geometry, Properties, and Product Selectivity of a Nonclassical Carbene

“…Cyclobutylcarbene ( 1 ) − is a deceptively simple carbene. − Indeed, only a few laboratory experiments claim its intermediacy (see Supporting Information; Schemes S1–S3). − Three main C 5 H 8 products have been attributed to thermolytically generated 1 (Scheme ): ,,, bicyclo[2.1.0]­pentane ( 2 ; housane), − cyclopentene ( 3 ), − and methylenecyclobutane ( 4 ). − The C 5 H 10 compounds methylcyclobutane ( 6 ) and 1-pentene ( 7 ) were also noted. , The intermediacy of 1 during the UV photolysis of 2 and 3 has been suggested as well. , Regrettably, none of the methods guarantees a carbene reaction intermediate. For instance, procedures relying on the in situ formation of Bamford–Stevens reactants, , such as cyclobutanecarbaldehyde p -tosylhydrazone alkali salts, could yield alkene 4 directly, via a Shapiro olefination, , or form alkane 6 via a Wolff–Kishner–Huang , reduction . Furthermore, 6 and 7 likely stem from the (cyclobutyl)­methyl radical ( 5 ), formed by triplet-state carbene 3 1 (Scheme ).…”

“…20,21 Regrettably, none of the methods guarantees a carbene reaction intermediate. For instance, procedures relying on the in situ formation of Bamford−Stevens reactants, 35,36 such as cyclobutanecarbaldehyde p-tosylhydrazone alkali salts, 19 could yield alkene 4 directly, via a Shapiro olefination, 37,38 or form alkane 6 via a Wolff−Kishner−Huang 39,40 reduction. 19 Furthermore, 6 and 7 likely stem from the (cyclobutyl)methyl radical (5), 41 formed by triplet-state carbene 3 1 (Scheme 1).…”