Molecular recognition cycloaddition

Recent research deals with stereoselective 1,3-dipolar cycloadditions of nitrones for the syntheses of alkaloids and aza heterocycles asymmetric synthesis of biologically active compounds such as glycosidase inhibitors, sugar mimetics, /3-lactams, and amino acids synthesis of peptido-mimetics and peptides chemistry of spirocyclopropane heterocycles synthesis of organic materials for molecular recognition and photochemical applications. 

PM3 calculations of the 2 + 3-cycloaddition of t-butylphosphaacetylene with 2,4,6-triazidopyridine are consistent with the dipole-LUMO-controlled reaction type. An FTIR spectroscopic study of the 1,3-dipolar cycloaddition of aryl azides with acetylenes shows that the rate of reaction increases logarithmically with pressure (below 1 GPa). The 3 -I- 2-cycloaddition between an azide (69) and a maleimide (70) has been greatly accelerated by utilizing molecular recognition between an amidopyridine and a carboxylic acid [see (71)] (Scheme 24). ... 

Another important issue related to surface cycloaddition reactions is the stereochemistry of the products. Advances in this area may open new methods for developing new chemical sensors that may be used for complex molecular recognition tasks. In one study, Wolkow and coworkers54 showed that a scanning tunneling microscope can be used to determine the absolute chirality of individual molecules of cis- and trans-2-butene adsorbed on... 

Mixtures of coumarin and thymine undergo cycloaddition on irradiation in the presence of a molecular recognition catalyst. The reaction affords two cross adducts identified as the cis,syn- and the cis,anti-adducts 1,3-Dimethyluracil... 

Binder and Kluger [41, 42] utilized the Hamilton wedge and THY as molecular recognition handles in the construction of side-chain-functionalized poly(oxanorbornene dicarboximides) using a ROMP/click methodology. Monomers functionalized with azido or alkynyl side chains were polymerized to either homopolymers or block copolymers and subsequently subjected to Cu-catalyzed azide-alkyne cycloaddition [72] to install the desired H-bonding motifs. 

Perfluoropropene and perfluorobutene-2 react with benzyl azide at 150 °C to give the [3+2] cycloadducts in 85% and 65% yields, respectively. Trimethylvinylsilane also undergoes the [3+2] cycloaddition reaction with 4-nitrophenyl- and 4-cyanophenyl azide to give the triazolines in high yields. Also, ]V-alkylmaleimides react with trimethylsilyl azide to give the corresponding [3+2] cycloadduct . The reaction of maleimide A -proponic acid and a heterocyclic azide is accelerated by molecular recognition . The palladium-catalyzed reaction of alkenyl bromides with sodium azide in dioxane at 90 °C or DMSO at 110 °C affords the 4-substituted 1,2,3-triazoles 55. ... 

Jurczak has shown that cycloaddition reactions involving furan could also be catalyzed by transfer RNA under high pressure [13]. Flence, kinetin 9 reacts with maleic anhydride and dimethyl acetylene dicarboxylate (DMAD) at lOkbar showing that tRNA is a true Diels-Alderase (Scheme 2). These products are not formed at high pressure without tRNA. It seems that a conformation of tRNA induced at high pressure meets structural requirements of a transition state of Diels-Alder reaction. It provides complementarity of size and shape of both substrates and is a driving force in molecular recognition. 

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