Tetramethylguanidine-[bmim][BF4]. An Efficient and Recyclable Catalytic System for One-Pot Synthesis of 4H-Pyrans

Beyond enzymatic promiscuity: asymmetric induction by l-proline on lipase catalyzed synthesis of polyfunctionalized 4H-pyrans

“…To the best of our knowledge, this kind of co-operative bio-organocatalysis has not been reported in the literature. 60 The fact that cooperative catalysis was observed in case Lproline with PPL, we sought to study whether other amino 65 acids also can cooperatively induce stereoslectivity with PPL for the pilot reaction. To this effect, we screened some amino acids at our disposal and the results are summerized in the Table 5.…”

“…Although baker's yeast is known to catalyze many stereoselective reactions, 31-33 the authors did not report any such observation. The fact that there are scant reports on stereoselective synthesis of polyfunctionalized 4H-pyrans, we 60 wanted to explore the catalytic effect of the lipase from Procine pancreas (PPL) on the synthesis of polyfunctionalized 4H-pyrans and its selectivity. The role of solvents and additional amino acids in the lipase catalyzed reaction was also explored in inducing stereoselectivity of this 65 otherwise promiscuous catalysis (Scheme 1).…”

“…The first and only asymmetric synthesis of polyfunctionalized 4H-pyrans via Michael was demonstrated by Gonzalaz et al starting from a chiral aldehyde which controlled the60 stereochemistry of the product in a two-step mechanism.…”

An Efficient and Facile Synthesis of 2‐Amino‐4H‐pyrans &Tetrahydrobenzo[b]pyrans Catalysed by WEMFSA at Room Temperature

“…Generally, 2‐amino‐4 H ‐pyrans are prepared by the one‐pot cyclocondensation of an aromatic aldehyde, malononitrile and ethyl acetoacetate as a β‐dicarbonyl compound in the presence of a basic catalyst. Various catalytic systems have been demonstrated for their synthesis, however very few reports on basic catalyst listed are; tetrabutylammonium bromide, hexadecyltrimethylammonium bromide, ( S )‐proline, Mg/La mixed oxide, MgO, Tetramethylguanidine‐[bmim][BF 4 ] and some of the new catalysts reported recently such as BNFe 3 O 4 , Ce−V/SiO 2 , and PPh 3…”

Ceria–Vanadia/Silica‐Catalyzed Cascade for C−C and C−O Bond Activation: Green One‐Pot Synthesis of 2‐Amino‐3‐cyano‐4H‐pyrans

“…[12] A large number of molecules bearing the pyranm oiety display aw ide-ranging spectrum of pharmacological activities in conditions such as asthma, hypertension, urinary diseases, andi schemia, and currently,many are in use in the treatment of variety of diseases. [22][23][24][25][26] Thus, the synthesis of substituted pyran derivatives has been the topic of many research investigations, and severala pproaches have been pursued using variousc atalysts, including hexamethylenetetramine-bromine (HMTAB), [27] H 6 P 2 W 12 O 62 .H 2 O, [28] rare-earth perfluorooctanoate (RE(PFO) 3 ) , [29] phenylboronic acid, [30] silica-gel-supported polyphosphoric acid (PPA-SiO 2 ), [31] per-6-amino-b-cyclodextrin, [32] l-proline, [33] 4-dimethylaminopyridine( DMAP), [34] 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim[BF 4 ]), [35] MNP@P [imEt][Br], [36] tetra-n-butylammonium fluoride (TBAF) [37] amongst others. However, many of these procedures have one or more drawbacks such as moderate yields, requirement of expensive reagents, toxic organic solvents, stoichiometric catalysts, extreme reaction conditions, lengthy procedures,o rl ong reactiont imes,.…”