Dithioacetal Group Research Articles

Recent developments of ketene dithioacetal chemistry

Ketene dithioacetals are versatile intermediates in organic synthesis. Extensive research, since the last decade, has given rise to new prospects in their chemistry. The objective of this review is twofold: first, to highlight the new prospects in the chemistry of functionalized ketene dithioacetals, and second, to provide an intrinsic link between ketene dithioacetal groups and a variety of other functional groups, which has brought out many new facts that will assist in future designs.

ChemInform Abstract: Generation and Intramolecular Cyclization of Free Radicals at the Carbon Between Two Heteroatoms under Non-Reductive Conditions.

Abstract Dithioacetal group was found to be a good radical generating group in the presence of photo-excited benzophenone and the resulting radical could be trapped in the intramolecular manner to give cyclopentanone and cyclohexanone derivatives.

Crystal and molecular structure of the β-anomer of 6,7-dideoxy-1,2;3,4;9,10-tris-O-(1-methylethylidene)- d-erythro-α-d-galacto-undecopyranosid-8-ulose

6,7-dideoxy-1,2;3,4;9,10-tris-O-(1-methylethylidene)-d-erythro-α-d-galacto-undecopy- ranosid-8-ulose, 3, was formed by adding a D-galactose-derived dithiane nucleophile to a protected erythronolactone followed by reductive removal of the dithioacetal group. Its β-anomer crystallizes in the chiral trigonal space group P3221 with a=b=12.2649(19) A, c=24.675(8) A, and Z=6. The molecule is composed of an erythrofuranose and a galactopyranose moiety, linked by a flexible ethylene bridge. The pyranose part of the molecule is disordered over two positions with equal occupancy. The configuration of the two disordered moieties is the same and they are converted into each other by a slight rotation of 6 degrees around one of the C–C single bonds of the ethylene bridge. The disorder allows for a more effective packing in the solid state.

Mechanistic investigation of hydrolysis reactions of dithioacetal derivatives grafted on silica gels

Silica gels believed to be grafted with dithioacetal derivatives were recently used for Hg(II) extraction, and were found to selectively remove 94–100% of Hg2+ ions from metal ion mixtures. The current studies with one derivative suggest that the functional group in the Hg(II) removal is the mercapto (SH) ligand. The dithioacetal group in (ClCOCH2S)2CHPh (2) was hydrolyzed during its reaction with amine (O)3Si(CH2)3NH2 (3) grafted on silica gel to give the mercapto ligand (O)3Si(CH2)3NHCOCH2SH (4). The silica gel grafted with the mercapto ligand 4 selectively removed Hg2+ ions with reported high capacities.

Oxidative Cyclization Based on Reversing the Polarity of Enol Ethers and Ketene Dithioacetals. Construction of a Tetrahydrofuran Ring and Application to the Synthesis of (+)‐Nemorensic Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Anodic Olefin Coupling Reactions Involving Ketene Dithioacetals: Evidence for a “Radical‐Type” Cyclization.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Anodic olefin coupling reactions involving ketene dithioacetals: evidence for a ‘radical-type’ cyclization

A series of anodic coupling reactions between ketene dithioacetal groups and enol ethers have been studied in order to probe why some of the cyclizations are successful while other closely related attempts fail. It has been found that the success of the cyclization reactions strongly depends on the location of substituents on the olefins. The reactions are highly sensitive to substituents on the terminating olefin but not to substituents on the initial radical cation. This behavior is consistent with what has been observed previously with radical cyclization reactions.

Oxidative cyclization based on reversing the polarity of enol ethers and ketene dithioacetals. Construction of a tetrahydrofuran ring and application to the synthesis of (+)-nemorensic Acid.

The utility of oxidative cyclization reactions for the construction of tetrahydrofuran rings has been examined. In these experiments, alcohol nucleophiles were found to be effective traps for radical cation intermediates generated from both enol ether and ketene dithioacetal groups. The reactivity of the alcohol trapping group appeared to lie between that of an enol ether and an allylsilane trapping group. The stereochemical outcome of cyclization reactions originating from the oxidation of an enol ether was found to be controlled by stereoelectronic factors. The utility of these cyclization reactions was illustrated with the synthesis of a key tetrahydrofuran building block for the synthesis of linalool oxide and rotundisine. Cyclization reactions triggered by the oxidation of a ketene dithioacetal led to far greater levels of stereoselectivity. The stereochemical outcome of these reactions was shown to arise from steric factors involving the larger ketene acetal group. The synthetic utility of cyclizations utilizing ketene dithioacetal derived radical cations was demonstrated by completing an asymmetric synthesis of (+)-nemorensic acid. Finally, the reactions were shown to be compatible with the use of an amide nucleophile and the direct formation of a lactone product.

ChemInform Abstract: Anodic Cyclization Reactions: Reversing the Polarity of Ketene Dithioacetal Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Anodic oxidations of electron-rich olefins: radical cation based approaches to the synthesis of bridged bicyclic ring skeletons

Abstract The use of intramolecular anodic olefin coupling reactions for building bicyclo[3.2.1]octane ring skeletons has been examined. While simple model systems using bis enol ether substrates readily led to the formation of bicyclic products, application of the reactions to total synthesis efforts were hindered by reactions forming dimethoxy acetal groups at both the terminating and initiating ends of the cyclization reactions. In an effort to solve this problem, ketene acetal based initiating groups have been studied. The use of a ketene dithioacetal group proved especially useful for this purpose.

Anodic cyclization reactions: reversing the polarity of ketene dithioacetal groups.

Intramolecular coupling reactions of ketene dithioacetal groups with enol ether and alcohol nucleophiles have been studied. The reactions were initiated by an anodic oxidation of the ketene dithioacetal and proved to be compatible with the formation of five- or six-member rings, as well as the stereoselective generation of quaternary carbons.

SYNTHESIS OF (6-2H)- AND 6-DEOXY-6-FLUORO-L-GALACTOSE DERIVATIVES11

The selective oxidation of trimethylsilylated D-galactose diethyl dithioacetal using Collins reagent provided the corresponding D-galacto-hexo-dialdo dithioacetal. Successive acid hydrolysis, isopropylidenation, and cleavage of the dithioacetal group gave the 1,2;3,4-di- O-isopropylidene-L-galacto-hexodialdo-1,5-pyranose as a key intermediate for the synthesis of 6-fluoro-and 6-deutero-substituted L-fucose derivatives. 1 Dedicated to Professor Peter Köll on the Occasion of His 60th Birthday.

Intramolecular 1,3-dipolar cycloadditions of 5-azido-5-deoxyaldopentose ketene dithioacetal bis(sulfones) in the synthesis of imino sugar analogs

Oxidation of the dithioacetal groups in the O-acetylated 5-azido-5-deoxy dibenzyl dithioacetal 3 of D-xylose and that ( 7) of D-ribose leads to triazoline derivatives 4 and 8, the products of sequential oxidation to the bis(sulfones), loss of AcOH between C-1 and C-2 and, spontaneous intramolecular 1,3-dipolar cycloaddition of an azido ketene intermediate. A possible explanation of the observed diastereoselectivity is discussed.

Ketene dithioacetal as a π-electron donor in second-order nonlinear optical chromophores

It is shown experimentally that the ketene dithioacetal group is very effective as an electron-donating group in the design and synthesis of thermally stable and efficient second-order nonlinear optical chromophores.

Reversing the Regiochemical Course of 1,3-Dipolar Cycloaddition of Nitrile oxides by Modification of Dipolarophiles

The orientation of the cycloaddition of nitrile oxide to β-substituted-α,β-unsaturated aldehyde equivalents was directed by choice of the carbonyl protective group, both of the two possible regioisomers of 2-isoxazolines were selectively prepared. Cycloaddition to the acetal derivatives preferentially gave the regioisomer bearing acetal group on C(4) position. While the opposite regioselectivity was observed for the cycloaddition to dithioacetal derivatives, where the sulfur functional group was mainly located at C(5) position. Theoretical studies on these regiochemical courses showed the C(5) orientation of dithioacetal groups to be directed by steric control, whereas frontier orbital interaction controlled the C(4) orientation of the acetal groups.

Radical Copolymerization of 2-MEm-1,3-Dithiane with Styrene and Methyl Methacrylate

Abstract This paper describes radical copolymerization of 2-methylene-1, 3-dithiane (a six-membered cyclic ketene dithioacetal, 1) with styrene and methyl methacrylate (MMA), The copolymerization proceeded without ring-opening of 1 to produce copolymer having dithioacetal group. The structure of the copolymer was determined by 1H, 13C NMR, IR, and UV spectroscopies. Polymerizability of 1 was higher than that of styrene and MMA. Monomer reactivity ratios determined are r1 = 3.35 and r2 = 0.03 (M2 = styrene) or r1 = 4.12 and r2 = 0.08 (M2 = MMA). The refractive index values of the resulting copolymers were also measured.

13C NMR Substituent Parameters of Dithioacetal Groups in Benzene Derivatives. The σp+Values of Cyclic Dithioacetals

The 13C NMR spectra of forty-six cyclic dithioacetals and their derivatives have been studied. A set of shift parameters was established for each of these heterocycles as substituent. Based on the Hammett type correlation for substituted benzenes, the σP +values of cyclic dithioacetal groups have been determined.

Generation and intramolecular cyclization of free radicals at the carbon between two heteroatoms under non-reductive conditions

Dithioacetal group was found to be a good radical generating group in the presence of photo-excited benzophenone and the resulting radical could be trapped in the intramolecular manner to give cyclopentanone and cyclohexanone derivatives.

ChemInform Abstract: 1,3‐Anti Asymmetric Induction in Addition of Organotitanium Reagents to β‐Substituted Aldehydes with a Dithioacetal Group.

AbstractThe 2‐formyl‐1,3‐dithianes (I) are treated with various methylmetallic compounds under different conditions to give the hydroxyethyl derivatives (III).

1,3-Anti Asymmetric Induction in Addition of Organotitanium Reagents to β-Substituted Aldehydes with a Dithioacetal Group

Abstract β-Substituted aldehydes with a dithioacetal group at α-position realized remarkable 1,3-anti selectivity in addition of organotitanium reagents in acyclic systems.