1,3-Diyl trapping reaction

With the intent of exploiting the intramolecular 1,3-diyl trapping reaction, Little and Muller prepared azo compound 663 and decomposed the substance in refluxing acetonitrile (Scheme LXVI) Triquinane 664, isolated in 85% yield, was then degraded to a saturated ketone which was methylated in the angular position prior to olefination. 

More recently. Little has synthesized 667 during his studies of the applicability of 1,3-diyl trapping reactions to the construction of tricyclopentanoids Capitalizing on a reversal of the normal regioselective mode of these transformations which gives rise to linearly fused triquinanes, he decomposed diazene 670 in refluxing acetonitrile and immediately subjected the product mixture to a hydroboration-... 

During their studies on the stereochemistry of intramolecular 1,3-diyl trapping reaction as depicted in Scheme 13, Little and collaborators utilized the reductive decarboxylation in preparing the required compound 31.24 The usefulness of Barton decarboxylation was also realized by Braekman and colleagues during their studies on ichthyotoxic sesterterpenoids in providing the needed methyl ketone 32 from the carboxylic acid 33.25 Helmchen has developed an easy route to a stable... 

Diyl-Trapping Reaction (intra-molekular) E21c, 2991, 2995... 

Intramolecular 1,3-Diyl Trapping Reaction (3/ , 3a/ , 6a/ , 7aS )-2,3.3a,5,6,6a,7,7a-Octahydro-2,2-dimethyl-17/-cyclopenta aJpentalen-3-ol Typical Procedure24 ... 

The intramolecular diyl trapping reaction was studied in a variety of solvents (THF, MeOH, acetonitrile), and the diyl was generated both thermally and photochemically [14]. The photo-induced deazetation of 41 in methanol at -6 °C afforded the desired tricyclopentanoid 40 in an excellent 84% yield. The transition state model portrayed by 49 nicely rationalizes the stereochemical outcome. The solvent study revealed that its choice had essentially no effect upon the product ratio at any given temperature. However, we did discover that methanol, a solvent which had not been utilized previously in intramolecular 1,3-diyl trapping reactions, was very useful for low temperature studies. 

Little, R.D. and Carroll, G.L. (1981) Intramolecular 1,3-diyl trapping reactions total synthesis of marine natural product ( )-A -capnellene. Tetrahedron Lett., 22, 4389-4392. 

Leonetti, J. A. Gross, T. Little, R. D. Cycloaddition-fragmentation as a route to bicydic ring systems. Use of the intermolecular diyl trapping reaction./. Org. Chem. 1996, 62, 1787-1793. 

Table 5 Ring Junction Stereoselectivity in Intramolecular Diyl Trapping Reactions OH...

In ter molecular 1,1-Diyl Trapping Reaction Reaction of 7-Isopropylidene-2,3-diazabicyclo[2.2.1 hept-2-ene and Dimethyl ( )-Butenedioate Typical Procedure6 ... 

A second example of diastereoselection in intramolecular diyl trapping reactions is provided by diazene 12 (Tabic 2, entry 18)31. Heating to reflux in acetonitrile gives 85% of a single fused tricyclic product. In this process, two stereocenters control the formation of four new stereocenters. 

It is possible to predict both the relative and the absolute stereochemical outcome of diyl trapping reactions [27] (Scheme 9). The preferred stereochemical outcome... 

ABSTRACT In this chapter we describe the development and application of the intramolecular diyl trapping reaction (cycloaddition) to the total synthesis of hirsutene, capnellene, coriolin, and hypnophilin, as well as its application toward the synthesis of aphidicolin and an analog of taxol . 

LINEARLY FUSED TRICYCLOPENTANOIDS. DIYL TRAPPING REACTIONS. 

The intermolecular diyl trapping reaction provides a direct and simple route to the linearly fused tricyclopentanoid ring system. As illustrated in the first example of this pathway, heating the dimethyl diazene 9 to 70-75 °C in the presence of an excess of cyclopentenone afforded a 90-98% yield of cycloadducts 10-12 [4].Unfortunately, the process displayed... 

The opportunity to conduct a diyl trapping reaction depends upon the availability of bicyclic azo compounds to serve as the diyl precursor. A basic approach to these systems consists of fulvene formation [5], Diels-Alder cycloaddition, selective saturation of the A-5,6 pi bond, and conversion of the biscarbamate to the diazene linkage,[6] as depicted in Fig. (3). 

With diazene 19 in hand, we were in a position to explore the first intramolecular diyl trapping reaction. These transformations are exceptionally easy to conduct, simply requiring heating or photolysis, removal of the solvent and isolation of the product(s). As with many diyl trapping reactions, the course of the process was monitored by TLC, reflux being discontinued when the diazene was consumed. In this... 

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