Dimethylamine as the key intermediate generated in situ from dimethylformamide (DMF) for the synthesis of thioamides

• Weibing Liu,
• Cui Chen and
• Hailing Liu

Beilstein J. Org. Chem. 2015, 11, 1721–1726, doi:10.3762/bjoc.11.187

• ., Haidian District, Beijing 100875, P. R. China; Tel: +86-15010928428 10.3762/bjoc.11.187 Abstract An improved and efficient method for the synthesis of thioamides is presented. For this transformation, dimethylamine as the key intermediate is generated in situ from dimethylformamide (DMF). All the tested

• substrates produced the desired products with excellent isolated yields. Keywords: aldehydes; dimethylformamide (DMF); elemental sulfur; ketones; thioamides; Introduction Thioamides, a well-known structural element of many sulfur-containing molecules, synthetic agents [1][2], heterocycles, natural products

• , our group has developed an improved synthetic procedure to construct thioamides (Scheme 1). Results and Discussion Our initial efforts focused on the optimization of the reaction conditions by employing 4-methoxybenzaldehyde (1a) as a model reactant to interact with elemental sulfur and DMF (Table 1

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• of these Michael acceptors and the low inherent nucleophilicity of the metal alkynylides. In 2010, Shibasaki and co-workers developed the asymmetric 1,4-addition of terminal alkynes to α,β-unsaturated thioamides [192]. In order to achieve this reaction, Shibasaki and co-workers used a soft Lewis acid

• agonist AMG 837 [199]. Shibasaki and co-workers expanded their application of soft Lewis acid/hard Brønsted base cooperative catalysis to the asymmetric vinylogous conjugate addition of α,β-unsaturated butyrolactones to α,β-unsaturated thioamides [200]. This reaction provides a method for producing

• enantioenriched butenolide units, which are found in many natural products [201][202][203][204] (Scheme 24). The reactions in Scheme 24 demonstrate that the vinylogous conjugate addition of unsaturated butyrolactones to α,β-unsaturated thioamides proceeded in high yields, enantioselectivities and

A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions

• Murugan Sathishkumar,
• Sangaraiah Nagarajan,
• Poovan Shanmugavelan,
• Murugan Dinesh and
• Alagusundaram Ponnuswamy

Beilstein J. Org. Chem. 2013, 9, 689–697, doi:10.3762/bjoc.9.78

• environmentally friendly methodologies for the synthesis of 2-iminothiazolidin-4-ones is worth attempting. In this regard, and in continuation of our recent reports on the solvent-free synthesis of amides [19][20], thioamides [21], cyclic imides [22], thiazolidin-4-ones [23], spirothiazolidin-4-ones [24], 1,2,3

The Eschenmoser coupling reaction under continuous-flow conditions

• Sukhdeep Singh,
• J. Michael Köhler,
• Andreas Schober and
• G. Alexander Groß

Beilstein J. Org. Chem. 2011, 7, 1164–1172, doi:10.3762/bjoc.7.135

• in various different synthesis strategies. The reaction proceeds smoothly if S-alkylated ternary thioamides or thiolactames are used. In the case of S-alkylated secondary thioamides or thiolactames, the Eschenmoser coupling needs prolonged reaction times and elevated temperatures to deliver valuable

• yields. We have used a flow chemistry system to promote the Eschenmoser coupling under enhanced reaction conditions in order to convert the demanding precursors such as S-alkylated secondary thioamides and thiolactames in an efficient way. Under pressurized reaction conditions at about 220 °C, the

• in the separation of the desired product from phosphine sulfide byproducts. S-Alkylated ternary thioamides of type 7 usually undergo the episulfide formation and subsequent sulfide contraction smoothly (Scheme 2). This is due to the strong electron accepting nature of the thioiminium intermediate 8