Syntheses by Other Groups

The following sections give an overview of the total syntheses of kelsoene that have been reported by other groups. With respect to the key step by which the tricyclic framework is constituted, they can be divided into two groups, the [2-1-2]-photocycloaddition approach and the homo-Favorskii strategy. 

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In recent years, PAMAM on polystyrene was also synthesized by other groups. " A similar methodology was used by Wang and coworkers to assemble PAMAM dendrons on multilayer microspheres consisting of a magnetite core covered by an intermediate methyl methacrylate-divinylbenzene polymer shell and polyglycidyl methacrylate outer layer (Scheme 15.12)." ... 

The title compounds kelsoene (rac-l) and (+)-preussin (2) have recently been synthesized in our laboratories using a stereoselective photochemical reaction as key step (Fig. 1). It is the purpose of this review to give a more detailed account on this work. In addition, other successful synthetic strategies to kelsoene and preussin will be comprehensively discussed. This intention has defined the way the content of the review was arranged. In two individual sections the target molecules are presented. Each section provides a short introduction to the target, a review on the syntheses conducted by other groups and finally an account of our own contribution. 

This sequence of reactions was later repeated3 with 2,6-lutidyl-lithium to give the corresponding 6-methylquinolizinium ion in improved yield. Several related syntheses based on this pattern were reported by other groups of workers4,5,6 soon after. Richards and Stevens4 reported the formation of 2-ethyl-3-methylquinolizinium... 

An interesting extension of this Mannich reaction was reported very recently by the Barbas group [26]. An a-imino glyoxylate 33 was used as a (preformed imine) starting material. The corresponding Mannich reaction furnished directly functionalized a-amino acids of type (S)-34 (see also the selected example in Scheme 5.15) which are difficult to synthesize by other synthetic routes. 

The practicality of the method was enhanced by the fact that simple extraction provided access to both the hemiester product and the alkaloid without chromatography, and the recovered cinchona alkaloid could be reused with no deterioration in the ee or yield of the reactions. This method has found use by other groups in the synthesis of / -amino alcohols and in natural product synthesis [173, 174], and has recently been reported as an accepted method in Organic Syntheses [175]. 

From 1990 to 1997, a number of chromophores with ever improving pp values were synthesized by research groups led by Alex Jen, Seth Marder, Tobin Marks, Tony Garito and many others [2, 3, 5, 63]. Unfortunately, these chromophores did not translate to materials with ever-increasing electro-optic activity. Thus, as late as 1997, it was not clear that any organic material had surpassed the elec-... 

Among the various other categories of nanoparticles synthesized by research groups or companies, some have been combined with different FR agents and the fire behavior of the host polymers has been evaluated. 

Xenon tetrafluoride forms stable colorless crystals. Two other xenon fluorides, XeF2 and XeFs, were synthesized by the group at Argonne, and a highly explosive xenon oxide (XeOy) was also found. The xenon fluorides react with water to form hydrogen fluoride and oxycompounds. For example ... 

As active metal complexes are mostly too large to enter the molecular sieve pores they have to be synthesized in situ via the so called ship-in-bottle procedure, first described by Romanovsky in 1984 [220] and subsequently adopted by other groups [ 196,221,222,223]. 

In addition to previously described syntheses by diazo group transfer with deformylation, 2-diazocyclohexanone has been prepared by two variants of this method. In one, the reaction of 2-(hydroxymethylene)cyclohexanone with jJ-toluene-sulfonyl azide is carried out in ether/diethylamine, and an enamine is assumed to be formed as an intermediate in the other, the sodium salt of the hydroxymethylene compound was treated with the lithium salt of jj-carboxybenzenesulfonyl azide... 

Some of the proposed species, such as Eg for E = Sn, Pb and Pn " for Pn = As, Sb, were structurally characterized later by other groups, while the existence of other proposed species, for example Pb, Bi, Pn , Png" for Pn = As, Sb, Bi, was never confirmed. Nonetheless, the recently synthesized mixed-... 

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