N-Boc-aminals as easily accessible precursors for less accessible N-Boc-imines: facile synthesis of optically active propargylamine derivatives using Mannich-type reactions

N,N‐Diacylaminals as Emerging Tools in Synthesis: From Peptidomimetics to Asymmetric Catalysis

“…Under these conditions, chiral Brønsted acid-catalyzed Mannich reactions of alkynyl N-Boc imines proceeded effectively with acetylacetone, [29b] and with cyclic and acyclic b-keto esters able to produce sufficiently highe nol concentrations for the reactiont op roceed (Scheme 7). [34,35] Interestingly,w hen aldehydes are used in this reaction, a dual activation of the aldehyde and the alkynyl N-Boc imine was observed under Brønsted acid catalysis. [36,37] The authors proposed that tert-butyl carbamate, released in the generation of the N-Boc imine, reacts with the aldehyde to generate the correspondingnucleophilic enecarbamate (Scheme 8).…”

Metal-free multicomponent approach for the synthesis of propargylamine: a review

“…Taking exactly same coupling component set in stoichiometric ratio Lee et al 41 synthesized propargylamines in water using a continuous ow, 48 reaction system (Scheme 4), which is a good alternative of lower efficiency batch reactors, 49 for industrial preparation of propargylamines without the requirements for large scale reactors. The high surface area to volume ratio may be the cause of high efficiency of this protocol providing efficient heat and mass transfer, which allowed the reaction at higher temperature (140 C) than 100 C. Water solubility of the reactant component was the major issue in this reaction.…”

“…Wang and his group, 40 N-Boc aminal 62, 68 is a good choice for the synthesis of optically active propargylamine derivatives (65, 66, 67) and this was developed by Maruoka and his co-workers. 41 Less accessible N-Boc imine can be in situ obtained from more accessible N-Boc aminal under acid medium before it was made to react with various carbon nucleophile such as aldehyde 41a, b-keto ester 64, 1,3-diketones 63 having a-H atom (Scheme 25) in presence of chiral phosphoric acid catalysts (68-71, Fig. 3).…”

“…27 There are only a few reports published in the literature describing the A3 and other MCR (multicomponent reaction) for the metal-free propargylamine synthesis. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] From the green and sustainable point of view, metal-free synthesis is the best eco-friendly approach while assessing environmental safety. The object of green chemistry mainly focuses on the development of novel methodologies and alternative sustainable synthetic strategies, which must include the environmental considerations.…”

Direct asymmetric N-propargylation of indoles and carbazoles catalyzed by lithium SPINOL phosphate

“…Besides these, there are several other challenges for the catalytic enantioselective C-N bond formation between indoles and carbazoles, and C-alkynyl N,O-acetals. C-alkynyl N,N-aminals have been reported to react with EtOH to form the corresponding Calkynyl N,O-acetals 61 . Thus, unlike the products generated by Cbased nucleophiles, for the products produced by N-centered nucleophiles, there is a risk of a direct conversion of newly formed C-alkynyl N,N-aminal products back to the C-alkynyl N, O-acetals (starting materials).…”