Iodine as a mild and efficient catalyst for the diastereoselective synthesis of δ-silyloxy-γ-lactones

The Vinylogous Aldol and Related Addition Reactions: Ten Years of Progress

“…Several papers appeared in the period covered by this review, which were mainly focused on the viability and simple diastereoselectivity control of VMAR involving furan- and pyrrole-based dienoxy silanes and aromatic or aliphatic aldehydes. Scheme lists four representative reactions selected from independent studies where furan-based VMAR was conducted using diverse Lewis acid promoters. ,− In these instances it is clear how the nature of the Lewis acid impacts simple diastereocontrol with variable results, which are difficult to fully rationalize.…”

Graphite oxide as catalyst for diastereoselective Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan in solvent free conditions

“…The stereochemical outcome was determined by 1 H-NMR analysis on the crude products according to previous reports. [34] It is worth adding that this diastereoselective control in so mild and convenient conditions is quite surprising based on that reported in literature [22,23,27]. In fact the use of metal catalysts ,very low temperature and often toxic solvents, is usually necessary to obtain good results both in efficiency and stereoselectivity, representing a limit for application of already known procedures in a sustainable context.…”

“…[14,15] In particular, the catalytic coupling of 2-(trimethylsilyloxy)furan with aldehydes in presence of Lewis acids is one of the most efficient method for the synthesis of -hydroxy--unsaturated--lactones, versatile building block for the synthesis of several biologically active natural products. [16][17][18] Lewis acids such as BF 3 -OEt 2 , TMSOTf, ZnCl 2 , TiCl 4 , SnCl 4 , SiCl 4 [19][20][21] or recently bismuth triflate [22] and iodine [23] have been known to catalyse this reaction under strictly anhydrous conditions or to promote the reaction at very low temperature (-78°C). The use of metal incorporated mesoporous/zeolite materials were also reported as active heterogeneous catalysts, but the presence of metals and the use of toxic solvents can limit the application of these procedures.…”

Synthesis of multifunctionalized building blocks via vinylogous addition of Chan’s diene to carbonyl and carbonyl-related electrophiles, mediated by molecular iodine

“…In a recent paper, 8 iodine was proposed as a very efficient catalyst for Mukaiyama aldol addition of 2-(trimethylsilyloxy)furan to several aromatic and aliphatic aldehydes. Compared to other catalysts, iodine presents many advantages including that it is very inexpensive, has low toxicity and is readily available; moreover, short reaction times and operative simplicity (no special precautions in order to exclude air and moisture from the system are required) make iodine-mediated procedures particularly convenient.…”