Functionality latent

The Ugi reaction is the four-component condensation of an amine, aldehyde or ketone, carboxylic acid and isocyanide to give an o -acylamino amide [22-24], Although this process has the potential to introduce considerable diversity, the products themselves are not heterocycles but through appropriate choice of substrates, latent functionality in one of the precursors can intercept either an intermediate or further derivatize the acylamino amide Ugi product through post-modification. Thus variants of the Ugi reaction have been investigated under microwave-assisted conditions for the synthesis of diverse heterocyclic libraries [16,19-24],... 

Cyclobutenes have been applied as latent functionality of 1,4-dicarbonyl systems. Photolysis of (466) gave a 1.5 1 mixture (60%) of (467a) and (467b), which were cleaved by ozone and subsequent reduction of the ozonides yielded the epimeric (468). Cyclization and dehydration process converted (468) to the furan (469) 160). Furan (469) was converted to hibiscone C in a few steps, 60). 

Chemoselective control elements protecting and activating groups. Latent functional groups... 

For rather too broad a concept of "latent functionality", see D. Lednicer in "Advances in Organic Chemistry Methods and Results", Vol. 8, John Wiley Sons, 1972, pp. 179-293. 

In the upper right-hand corner of Figure 5-1, there is another subsystem (or subsystems) labeled Latent Functions. These are psychological potentials that we did not develop in the course of growing up in our culture, that may indeed have been strongly inhibited by the culture, but that are potentially available. These include the psi potentials. 

Synthon Some reagent equivalents (masked or latent functionality, LF) Page ref. 

The oxidation of furans has often been used to express the latent functionality present within this heterocyclic framework, and it results particularly attractive for the synthesis of the widespread butenolides [8c,56]. Dye-sensitized photo-oxygenation of furfural, furoic acid and a- or a,a -unsubstituted furans leads directly to butenolides [8c,56,60d,63]. The presence of a silyl group in a-position enhances the rate of endoperoxide formation and controls the regiochemical outcome of the second-step leading to the related butenolide via a rapid intramolecular silatropic shift [64]. An application of this reaction is shown in Sch. 39 as a step in the synthesis of spongianolide A, an antitumoral natural sestertepenoid [65],... 

These compounds have proven to be the most versatile building blocks for construction of other ynamines mainly through protonation, alkylation and acylation. Such reactions are called aminoethynylation 131). More recent development involves the use of stable stannyl ynamines. Lithio ynamines 44 are prepared in situ and alkylation is achieved by adding the corresponding alkyl halide or tosylate. The D3-ynamine 45 was prepared via the latter method (80) 132). Two selected examples (81, 82) where the acetylene chain carries a latent functionality follow 133,134). 

Different heterocyclic systems can undergo cleavage reaction that leads to a linear carbon skeleton with functional groups. The easier to get those systems, to modify them and to break them in several ways, the more their diversity. Two systems of cyclic oxime ethers that were studied in this connection are 2-isoxazoline and 1,2-oxazine. The former, which was obtained by 1,3-dipolar cycloaddition of a nitrile oxide, and a substituted double bond114, can be cleaved in several ways, in which the latent functions are revealed. One example in which a,/Lenoximes and enones114 are formed is shown in equation 43. 

For the synthesis of C-functionalised aza crowns, it is necessary to introduce the required (or latent) functionality prior to cyclisation. The most common aza crowns possess a C3 or C2 chain between the nitrogens and a variety of methods for introducing these subunits has developed. 

An example of an excellent latent functional group for this purpose is benzocyclobutene (BCB) [13]. Polystyrene made using a BCB functional peroxide leads to the formation of linear polystyrene because the BCB moieties are inert below 180°C. Once the polymer exits the polymerization reactor it is... 

An additional functionality that comes into play only when the reaction conditions are changed is called latent functionality. 

The prepolynier can be reacted further with a wide variety of reagents, and its latent Functionality depends on the particular reaction. The conversion of an epoxy polymer to an interconnected network structure is formally similar to the vulcanization of rubber, but the process is termed curing in the epoxy system. When the epoxy hardener is a primary or secondary amine like m-phenylene diamine the main reaction is... 

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