Thiocarbonyl Ylides. Attempted Preparation and Related Reactions

Abstract

The attempted preparation of thiocarbonyl ylides (I) by the proton abstraction of thiouronium salts (III) has disclosed a fast isomerization of I to enethiols (V) (Y=H) and an alternative desulfurization to enediamines (VII) (Y=Ph), the by-products being olefins (VIII) and sulfides (IX). The second route to I examined consists of the reaction of tetramethylthiourea (II) with diazomalonate, which gives rise to enediamine (VIIg). Rotation about the C=C bond of enediamines is discussed on the basis of IR and NMR spectra.

(3+2) Cycloadditions of Thiouronium Ylides: A Room-Temperature, One-Pot Approach to Dihydrothiophenes

“…Performing the reaction at higher or lower temperatures let to no product formation at all. This reduction in the stability of the thiocarbonyl intermediate has been investigated previously (in the absence of any coupling partner) by the group of Nozaki, and a number of decomposition pathways have been identified …”

“…Thiocarbonyl ylides, formally 1,3-dipoles, represent a conceptually distinct class of sulfonium ylides, with unique reactivity . Reactions involving thiocarbonyl ylides include electrocyclizations, dimerization-type reactions, 1,3 acid–base addition reactions, rearrangements, and cycloadditions. , A number of these transformations have been developed to the stage where they have found use as key steps in the syntheses of a number of natural products. ,, However, the high reactivity and instability of these compounds place some limitations on their synthetic utility, and reactions employing thiocarbonyl ylides often have to be very carefully designed . The synthesis of these ylides, almost always undertaken in situ for onward reactions, often requires either very high temperatures or cryogenic cooling. ,, One of the most common routes involves the use of alkyl azides, which restricts the scale on which these reactions can safely be undertaken.…”

Synthesis and properties of β,β-bisfunctionalised keteneN,N-acetals

“…Not only S-methyl derivatives of isothiouronium salts, but also compounds with more complex S-substituents can serve as starting compounds in the synthesis of ketene N,N-acetals. 59 Treatment of salts 41 containing an electron-acceptor group at the sulfur atom with sodium hydride in tetrahydrofuran gives enediamines 42 in moderate yields. It is believed 59 In the same study, 59 a method is proposed for the synthesis of ketene N,N-acetal 44 with the use of diethyl diazomalonate and tetramethylthiourea as the starting compounds.…”

“…59 Treatment of salts 41 containing an electron-acceptor group at the sulfur atom with sodium hydride in tetrahydrofuran gives enediamines 42 in moderate yields. It is believed 59 In the same study, 59 a method is proposed for the synthesis of ketene N,N-acetal 44 with the use of diethyl diazomalonate and tetramethylthiourea as the starting compounds.…”

The activating effects of arylazo groups on a double bond. Preparation and properties of some bis(diaikylamino)arylazoethenes and related compounds

“…Reactions of the azoalkenes (1) with some oxygen and sulphur nucleophiles were also investigated. 2-Methylaminothiophenol gave the addition-elimination products (7) in high yield. These compounds both absorb at long wavelength (Table ), presumably because the substituent donor groups are held in the plane of the acceptor group.…”