Unexpected reactivity of annulated 3H-benzothiazol-2-ylideneamines as an acyl transfer catalyst

Abstract

3,4-Dihydro-2H-9-thia-1,4a-diazafluorene (2b) was found to be an extremely effective catalyst, the reaction with which was faster than that with DMAP.

Nucleophilicities and Lewis Basicities of Isothiourea Derivatives

“…Equimolar amounts of (dma) 2 CH þ BF 4 À (16 mg, 0.047 mmol) and 7 (8.3 mg, 0.047 mmol) were mixed in d 6 -DMSO (0.6 mL) in an NMR tube under nitrogen and the NMR was taken after few minutes of shaking. 7P-BF 4 : 1 H NMR (d 6 Formation of 9P-BF 4 . To a blue solution of (dma) 2 CH þ BF 4 À (22 mg, 0.065 mmol) in CH 2 Cl 2 (1 mL) was added drop by drop a solution of 9 (9.2 mg, 0.062 mmol) in dry CH 2 Cl 2 (1 mL) under nitrogen at room temperature.…”

Isothiourea‐Mediated Asymmetric O‐ to C‐Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies

“…In the literature, amidines and isothioureas have been widely used to promote a range of asymmetric O-and Nacylation protocols, building upon the pioneering work of Birman [11] and Okamoto. [12] These readily prepared or comKeywords: asymmetric catalysis · isothioureas · Lewis bases · NMR spectroscopy · reaction mechanisms…”

“…[11d] Following the development of 3,4-dihydro-2H-pyrimidoA C H T U N G T R E N N U N G [2,1-b]benzothiazole 10 (DHPB) by Okamoto, [12] and their own studies, [11e] the Birman group developed homobenzotetramisole 11 (HBTM)…”

Amines vs. N‐Oxides as Organocatalysts for Acylation, Sulfonylation and Silylation of Alcohols: 1‐Methylimidazole N‐Oxide as an Efficient Catalyst for Silylation of Tertiary Alcohols

“…[11][12][13] Although some comparative studies have been reported for specific reaction types, e.g. for acylation [14][15][16][17] and for silylation [18] to the best of our knowledge, a comparative study of the relative abilities of the most commonly used N-heterocycles to catalyse acylation, sulfonylation and silylation of alcohols has not been reported. We considered that comparative data of this type would be valuable to allow selection of the optimal Lewis base for a given transformation and might also provide insight into preferred structural features for particular types of transformations.…”