Reagent schemes

Treating the iminothiazoles with acyl chlorides yields the aminium salts (415>, which are acylation and alkoxycarbonylation reagents (Scheme 237) (731). 

The condensation of a thiazolium with an oxonol dye in a basic medium is another example of the combination of electrophilic and nucleophilic reagents (Scheme 55). With a nonopening ring, the obtained neutrodimethine cyanine is not mesosubstimted (68). 

Other reactions that resulted in the formation of P=N double bonds are those of NH phosphinous amides with tetrahalomethanes [106-108]. The reaction products, P-halophosphazenes 19, may be further elaborated by substituting the halogen atom with amines or Grignard reagents (Scheme 19). 

Reduction of the Si-Si bond of oligosilanes with organo- or silyllithium reagents (Scheme 2.44, A,... 

Chiu et al. developed the first example of a reductive intramolecular Henry reaction induced by Stryker s reagent (Scheme 30) [53]. The conjugate reduction of keto-nitroalkenes with [Ph3PCuH]6 (150 mol%) triggers spontaneous nitro-aldol reaction at - 40 °C to produce (f-hydroxy nitro compounds in moderate yield. 

Traceless linker 60 based on a benzotriazole scaffold was reacted with amines and aldehydes to produce Mannich-type amine products [69]. Final product release was achieved by treatment with Grignard reagents (Scheme 29). 

Piperazine linker 77 was treated with propargyltriphenylphosphine bromide to provide a resin-bound Wittig reagent (Scheme 40) [89]. Base treatment followed by aldehyde addition produced a resin-bound 2-amino-butadiene which was implemented in [4 + 2] cycloadditions. Alternatively, treatment with 3% TFA in CH2CI2 released a,(J-unsaturated methylke-tones in high yields. 

Dialkylaminosulfur trifluorides are widely used as a safe substitute for SF4 in the replacement of oxygen by fluorine in many types of organic compounds, for example, converting alcohols to fluorides, or aldehydes and ketones to gem-difluorides. The most familiar of these reagents is DAST, while an increasingly popular one (considered safer to use than DAST) is bis(2-methoxyethyl)aminosulfur trifluoride (Deoxo-Fluor Reagent) (Scheme 7.15). 

The hydride-methyl complex OsH(Me)(CO)2(P Pr3)2 reacts with electrophilic reagents. The reaction products depend on the nature of the reagent (Scheme 39). Whereas the reaction with iodine gives almost quantitatively the diiodide OsI2(CO)2(P,Pr3)2, the reaction with a five-fold excess of phenylacetylene does not lead to the formation of the previously mentioned bis-alkynyl complex... 

For example, in the case of intramolecularly base-stabilized silanone 4 it was trapped by excess hexamethylcyclotrisiloxane to give the corresponding insertion product 5 but isolated as a trimer 6 in the absence of such a trapping reagent (Scheme 2).17... 

As discussed earlier, Ila, Junjappa and coworkers used cyclopropyl units as cation-provider in cationic domino processes. Within their interesting approach, the indole derivatives 1-170 could be converted into the unexpected carbazoles 1-171 with 54-69% yield in a five-step transformation using SnCl4 as reagent (Scheme 1.41) [48],... 

Heterocyclic phosphines 32 were prepared from base-induced condensation of a secondary 1,8-diamino-naphthalene with phosphorus trichloride (the corresponding As- and Sb-analogues were obtained analogously) and converted into cyclic phosphenium cations 33 by Lewis acid promoted halide abstraction using GaCl3 or trimethylsilyl triflate as reagents (Scheme 18) [15, 92],... 

Recently, a new method for synthesis of tertiary amines 326 from iV,iV-dialkyl O-benzoyl hydroxylamines 325 was proposed.425 The protocol is based on the copper-catalyzed reaction of hydroxylamines 325 with dialkyl- and diarylzinc reagents (Scheme 166). It is noteworthy that alkyl- and phenylzinc halides also reacted with compounds 325, however, yields were significantly lower than those for ZnR2 (18-29% vs. 69-98%). 

Similarly, a solid-supported imide has been reported to serve as an acylating reagent under microwave conditions by Nicewonger and coworkers [130], The starting imide was immobilized on aminomethyl polystyrene and in this case benzoyl chloride was chosen to prepare the acylating reagent (Scheme 7.111). Primary amines and piperazines were smoothly acylated at room temperature, but more hindered secondary amines required more time and higher temperatures, and anilines... 

A recent report [6] has discussed the effect of monomode microwave irradiation in the palladium-catalyzed phenylation of 5-iodouracil 4 with the nontoxic sodium tet-raphenylborate 5 as phenyl reagent (Scheme 8.3). The authors showed that the use of monomethylformamide (MMF) as solvent increases the yield of 6 (70%), because MMF has a high boiling point (180 °C) and is more polar (s = 182.5) than other amides used in microwave-activated reactions. 

In the preparation of novel 1,3,4-oxadiazoles 56 from 1,2-diacylhydrazines 55, Brain and coworkers [29] used a highly efficient cydodehydration assisted by use of micro-waves, in THF as solvent, using polymer-supported Burgess reagent (Scheme 8.21). 

Bose has described reactions between acid chlorides 214 and Schiff bases 215 where the stereoselectivity depends on the order of addition of the reagents (Scheme 9.68) [117]. When the condensation was conducted by a normal addition sequence (i.e. acid chloride last), only the cis /1-lactam (216b) was formed. However,... 

A series of nonracemic triorganotin hydrides (37-39) was prepared by reduction of racemic halostannane precursors with a chiral alkoxy hydride reagent (Scheme 14)21. 

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