Acetonyltriphenylphosphonium bromide and its polymer-supported analogues as catalysts in protection and deprotection of alcohols as alkyl vinyl ethers

Functionalised tetraarylstannanes Sn[C6H4-R]4 (R=–CH(CH2O)2, –CHO, –COOH, –CHN–NH–C6H3-2,4-(NO2)2, –CH2OH, –CO–NH–CH2–COO–CH3, –CH[N(C2H4)2O]2)

“…The first step of our reaction sequences was the synthesis of Sn[C 6 H 4 -CH(OCH 2 ) 2 ] 4 (2) by the interaction of tin tetrachloride with the Grignard reagent of p-bromobenzaldehyde-ethyleneacetal [11,12] (Scheme 1). The crude product obtained after filtration from the inorganic salt and after evaporation of the solvent was redissolved in CH 2 Cl 2 and precipitated again by addition of ethanol.…”

“…Tetraorganotin derivatives of the general formula Sn[C 6 H 4 -R] 4 (R ¼ para-substituent) [10] are stable under such conditions and have therefore found our interest. Representatives of such tetraorganotin derivatives carrying different organic functionalities in para-position like Sn[C 6 H 4 -CH(OCH 2 ) 2 ] 4 (2) and Sn 4 (3) have already been described by Drefahl and Lorentz [11] and Hon et al [12]. These compounds were so far only characterised by elemental analysis.…”

3,5-Dinitrobenzoic acid catalyzed synthesis of 2,3-unsaturated O- and S-glycosides and tetrahydropyranylation of alcohols and phenols

“…Importantly, no isomerization of double bond took place in case of eugenol (Table 2, entry 16). Although, several reports have appeared in the literature, [25][26][27][28][29][30][31][32][33] most of them suffer due to the use of expensive and moisture sensitive catalysts, high temperature, longer reaction times, and incompatibility with other functional groups, and some reagents also have to be prepared freshly prior to use. [25][26][27][28] In conclusion, we have developed a simple and convenient method for the synthesis of 2,3-unsaturated glycosides via the Ferrier rearrangement and tetrahydropyranylation.…”

A Highly Efficient Synthetic Protocol for Tetrahydropyranylation/Depyranylation of Alcohols and Phenols

“…Tetrahydropyranylation of alcohols or phenols is usually achieved by using pTsA, [2] BF 3 ·OEt 2 , [3] or PPTS. [4] Many other reagents, such as ZrCl 4 , [5] I 2, [6] LiBr, [7] acetonyltriphenylphosphonium bromide (ATPB), [8] TBATB, [9] aluminium chloride hexahydrate, [10] LiOTf, [11] In(OTf) 3 , [12] dialkylimidazolium tetrachloroaluminates, [13] InCl 3 immobilized in ionic liquids, [14] Bi(OTf) 3, [15] bromodimethylsulfonium bromide, [16] cupric sulfate pentahydrate, [17] and NbCl 5 , [18] have also been employed for both tetrahydropyranylation/depyranylation in recent years. Though metal triflates have been found to be effective catalysts for the above transformations, they still have some drawbacks, such as they are relatively expensive, difficult to handle, and not readily available.…”

“…[20] Unfortunately, many of these procedures have a disadvantage such as harsh reaction conditions, long reaction times, incompatibility with other acidsensitive functional groups, [3,9,10,13] the involvement of more expensive and moisture sensitive reagents, and some also have to be freshly prepared prior to use. [4,8,9,15,16] As part of our ongoing research to develop new synthetic methodologies by using various new reagents, [21][22][23] we realized that there is further scope for a cleaner and greener methodology for tetrahydropyranylation/depyranylation, one that might work under mild catalytic conditions and that is economically cheaper. In recent years, bismuth compounds have been gaining interest in various organic transformations.…”