An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation. Keywords: α-carboline; chemical diversity; inverse electron demand Diels–Alder; isatin; pyrido[2,3-b]indole; 1,2,4-triazine; Introduction In comparison with the well-known β-carbolines, α

• this design was the electron donation from the indole nitrogen into the isatin-derived triazine ring of 9, which would result in an elevated LUMO of the triazinyl azadiene, and thereby inhibit the desired cycloaddition. Thus, it was anticipated that an electron-withdrawing group R2, which could also

• serve as a diversification point, would be needed on the indole nitrogen. Results and Discussion Feasibility studies began with isatin-derived 1,2,4-triazine 9a (9, R1 = H) [73][74], which was easily prepared by the condensation of isatin (10, R1= H) with ethyl oxaloamidrazonate [75][76][77] (11) in

A general and facile one-pot process of isothiocyanates from amines under aqueous conditions

• Nan Sun,
• Bin Li,
• Jianping Shao,
• Weimin Mo,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2012, 8, 61–70, doi:10.3762/bjoc.8.6

• isothiocyanates – is still a challenge in organic chemistry. Results and Discussion Previously, Furumoto reported the application of cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, TCT) as a desulfurylation reagent in the synthesis of carbodiimides from thioureas under mild conditions [60]. In that reaction

• , the S-nucleophiles first reacted with TCT and then decomposed to release the product carbodiimides and by-product 2,4,6-trimercapto-1,3,5-triazine (TMT) [61]. Considering that TCT is an efficient desulfurylation reagent of thioureas to synthesize carbodiimides and that it is affordable in large scale

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• (Scheme 52) [79]. Other synthetic routes to 1,2,4-triazoles have also been reported. For example, the desired triazole ring of anastrozole can be obtained by reacting an appropriately substituted hydrazine hydrochloride salt 269 with triazine (270) (Scheme 53) [80]. It has been proposed that this novel

• transformation occurs by a two step process: Initially, a molecule of triazine undergoes condensation and ring cleavage with the hydrazine to generate formamidrazone 271 which then immediately reacts with a second molecule of triazine to yield the 1,2,4-triazole [81]. Hence, in this case the triazine can be

• considered as a formamide donor. Rizatriptan (76) has also been prepared by both the above mentioned procedures, i.e., via the pre-made triazole or by treatment of a hydrazine hydrochloride salt with triazine (Scheme 54) [82]. Indeed, the latter protocol has been further expanded to make use of additional

Synthesis of methylenebisamides using CC- or DCMT- activated DMSO

• Qiang Wang,
• Lili Sun,
• Yu Jiang and
• Chunbao Li

Beilstein J. Org. Chem. 2008, 4, No. 51, doi:10.3762/bjoc.4.51

• , when amides react with electrophile-activated DMSO, the yields are rather low. We have found new electrophiles, 2,4,6-trichloro[1,3,5]triazine (CC) and 2,4-dichloro-6-methoxy[1,3,5]triazine (DCMT), which activate DMSO in the presence of amides to yield methylenebisamides in good to fair yields. The

• amides can be aromatic or aliphatic. The operation is simple and the reagents are inexpensive. Keywords: amides; condensation; DMSO; methylenebisamides; 2,4,6-trichloro[1,3,5]triazine; Introduction Sulfoxides are activated by electrophiles to produce reactive sulfonium salts. These electrophiles

• on the chlorination [10] and etherification [11] of benzyl alcohols and from other references [12][13][14], we believe the reaction between 2,4,6-trichloro[1,3,5]triazine (cyanogen chloride, or CC) and DMSO produces a reactive sulfonium salt intermediate. Therefore, it was of interest to study the