Wet 2,4,6-trichloro[1,3,5]triazine (TCT) an efficient catalyst for synthesis of α,α′-bis(substituted-benzylidene) cycloalkanones under solvent-free conditions

Mild and efficient cyanuric chloride catalyzed Pictet–Spengler reaction

“…We envisaged that the use of cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, TCT) [38–45] as a source of HCl could trigger the 6- endo cyclization under dry and mild conditions. TCT is used in many reactions as a source of anhydrous HCl in organic synthesis [46]. Moreover, it is an attractive reagent due to its easy availability and low cost.…”

“…Moreover, it is an attractive reagent due to its easy availability and low cost. It is well documented in the literature that TCT reacts with the incipient moisture and produces three moles of HCl and cyanuric acid as a byproduct [46]. The latter can be removed by a simple aqueous workup.…”

Highly Selective Claisen–Schmidt Condensation Catalyzed by Silica Chloride Under Solvent-Free Reaction Conditions

“…[18] However, these reactions suffer from side reactions (such as self-condensation of ketones) and thus give poor yields of the desired products. Subsequently, more modified procedures have been developed that used Lewis acids and several other reagents such as Cp 2 TiPh 2 , [19] BMPTO, [20] RuCl 3 , [21] SmI 3 , [22] TMSCl=NaI, [23] TiCl 3 (CF 3 SO 3 ), [24] Yb(OTf) 3 , [25] [(Me 3 Si) 2 N] 3 Ln(mCl)Li(THF) 3 , [26] Al 2 O 3 =KF, [27] PEG400=K 2 CO 3 , [28] HT-OBU, [29] Mg(HSO 4 ) 2 , [30] InCl 3 , [31] FeCl 3 , [32] BF 3 Á OEt 2 , [33] molecular iodine (I 2 ), [34] Et 3 N in the presence of LiClO 4 , [35] LiOH, [36] trichlorotriazine (TCT), [37] NaOAc=HOAc, [38] and SOCl 2 = EtOH. [39] In spite of high-yielding products, many disadvantages such as the use of costly catalyst, hazardous agents like LiClO 4 and silica sulfuric acid, stoichiometric amounts of catalyst, and complicated purification operations have been encountered.…”

Solvent Free Synthesis of α, á-Bis(substituted-benzylidene)cycloalkanones Using Covalently Anchored Sulfonic Acid on Silica Gel (SiO<sub>2</sub>-R-SO<sub>3</sub>H) as an Efficient and Reusable Heterogeneous Catalyst

“…Such condensation reactions are also carried out in solvent-free conditions [23]. Silica sulfonic acid, nanoporous silica-based sulfonic acid and polymer supported sulfonic acid type catalysts are also employed for such condensations.…”