4298-75-3Relevant academic research and scientific papers
Oxidations of Thioketones by Singlet and Triplet Oxygen
Rao, V. Jayathirtha,Muthuramu, K.,Ramamurthy, V.
, p. 127 - 131 (1982)
Oxidation of di-tert-butyl thioketone (1) and 2,2,4,4-tetramethylcyclobutyl thioketone (2) by singlet oxygen yields the corresponding sulfine and ketone; in the case of 1 the sulfine is the major product, whereas in 2 it is the ketone. 1,2,3-Dioxathietane has been suggested as the precursor for the ketones, and the zwitterionic/diradical peroxide is believed to be a common primary intermediate for both sulfine and ketone.Steric influence is felt both during primary interaction between singlet oxygen and thioketone and during the partitioning of the peroxide intermediate.Steric interaction is suggested as the reason for variations in the product distribution between 1 and 2.Singlet oxygen is also generated through energy transfer from the triplet state of thioketones.These excited states also directly react with oxygen to yield ketone.
Cycloadditions of two thiocarbonyl ylides with α,β-unsaturated esters and nitriles: Steric course and mechanism
Huisgen, Rolf,Mloston, Grzegorz,Giera, Henry,Langhals, Elke
, p. 507 - 519 (2007/10/03)
In the probably concerted cycloadditions of the sterically hindered thiocarbonyl ylide 1 with fumaronitrile, maleonitrile, and dimethyl fumarate, the dipolarophile configuration is retained whereas retention/inversion 99:1 for dimethyl maleate (51 times less reactive than fumarate) signals a small involvement of a two-step pathway. The latter becomes dominant when two acceptor groups stabilize the anionic terminus of a zwitterionic intermediate. Nonstereospecific cycloadditions of 1 with dimethyl 2,3-dicyanofumarate (16, retention/inversion 60:40) and dimethyl 2,3-dicyanomaleate (17, 76:24) were observed. Special conditions were required to avoid a preceding cis, trans isomerization, 16?17, catalyzed by thiadiazoline 4, the precursor of 1. In the case of the related thiocarbonyl ylide 37, this catalysis could not be suppressed and the same ratio of adducts (55:45) was obtained with 16 and 17.
ALKYLATION OF KETONES BY USE OF SOLID KOH IN DIMETHYLSULFOXIDE
Langhals, Elke,Langhals, Heinz
, p. 859 - 862 (2007/10/02)
A mixture of solid KOH in dimethyl sulfoxide has a strong basicity, but only a low nucleophilicity and is used for α-methylation of ketones.With this simple and inexpensive reagent complete methylation with yields up to 90percent can be achieved.
Carbanionic Rearrangements of (Halomethylene)cycloalkanes
Samuel, Steve P.,Niu, Tian-qi,Erickson, Karen L.
, p. 1429 - 1436 (2007/10/02)
The mechanism for the unusual base-induced ring-enlargement reaction of (halomethylene)cyclobutanes to 1-halocyclopentenes was examined by C-13 labeling studies with (bromomethylene)cyclobutane (1), cis- and trans-1-(bromomethylene)-3-ethoxy-2,2-dimethylcyclobutane (15 and 16), and 1-(bromomethylene)-2,2,4,4-tetramethylcyclobutane (22).Two competing processes were found to lead from the vinyl anion to rearranged products: (1) rehybridization of the vinyl anion to a 1,2-carbene-anion, which subsequently undergoes rearrangement, and (2) a Beckmann-like simultaneousmigration of bromide and ring carbon.Both processes subtly bypass the "forbidden" alkyl-to-carbanion shift.
STERIC ASPECTS OF THE OXIDATION OF THIOKETONES BY SINGLET OXYGEN
Ramnath, Narayan,Jayathertha, Vaidhya Rao,Ramesh, Varadaraj,Ramamurthy, Vaidhyanathan
, p. 89 - 92 (2007/10/02)
Singlet oxygen oxidation of dialkyl thioketones yields the corresponding ketones and in some cases sulfoxides in varying amounts.Steric considerations on the reactive zwitterionic/diradical intermediates have been invoked to rationalise the product distribution.
