General Synthetic Route

The most general synthetic route to ketones uses the reaction of carboxylic acids (or their derivatives) or nitriles with organometallic compounds (M.J. Jorgenson, 1970). Lithium car-boxylates react with organolithium compounds to give stable gem-diolates, which are decom-... 

General synthetic routes to spiroketals 189 from lactones and lithiomethoxy-butenyne 184 have been described (83TL5303 88JOC652 89JOC1157 90JOC5894). Three synthetic schemes have been realized. 

Carbenes from Diazo Compounds. Decomposition of diazo compounds to form carbenes is a quite general reaction that is applicable to diazomethane and other diazoalkanes, diazoalkenes, and diazo compounds with aryl and acyl substituents. The main restrictions on this method are the limitations on synthesis and limited stability of the diazo compounds. The smaller diazoalkanes are toxic and potentially explosive, and they are usually prepared immediately before use. The most general synthetic routes involve base-catalyzed decomposition of V-nitroso derivatives of amides, ureas, or sulfonamides, as illustrated by several reactions used for the preparation of diazomethane. 

In 1978, Corey reported a general synthetic route for the conversion of alkenes to conjugated nitroalkenes via nitro-mercuration and demercuration.74 Since then, many chemists have used this method for the preparation of cyclic nitroalkenes such as 1-nitrocyclohexene. However, the use of mercury salts is not recommended even for the small-scale preparation of nitroalkenes. This reaction is not as clean as expected, and formidable efforts are required to remove the mercury in the waste. 

Methods for the synthesis of the biologically active dihydrodiol and diol epoxide metabolites of both carcinogenic and noncarcinogenic polycyclic aromatic hydrocarbons are reviewed. Four general synthetic routes to the trans-dihydrodiol precursors of the bay region anti and syn diol epoxide derivatives have been developed. Syntheses of the oxidized metabolites of the following hydrocarbons via these methods are described benzo(a)pyrene, benz(a)anthracene, benzo-(e)pyrene, dibenz(a,h)anthracene, triphenylene, phen-anthrene, anthracene, chrysene, benzo(c)phenanthrene, dibenzo(a,i)pyrene, dibenzo(a,h)pyrene, 7-methyl-benz(a)anthracene, 7,12-dimethylbenz(a)anthracene, 3-methylcholanthrene, 5-methylchrysene, fluoranthene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)-fluoranthene, and dibenzo(a,e)fluoranthene. 

A general synthetic route to p-lactam-fused enediynes (Scheme 2.321) has been successfully developed (848). When nitrone (771) was subjected to Kin-ugasa reaction conditions, two p-lactam containing products were obtained the elimination product (772) and the trans fused compound (773). 

Recently, a variety of reactions according to the general synthetic route shown in Scheme 7.32 were carried out, which facilitated a study of hydrocarbonyl-bridged gallium/zirco-nium compounds [173,174]. Two representative examples of these unusually structured R2Ga(g-R1,g-R2)ZrCp2 complexes will be described and discussed with regard to their structural properties [175]. 

SCHEME 2.4 General synthetic route or Gilch route to solution-processable PPV derivatives (From Gilch, H.G. and Wheelwright, W.L., J. Polym. Sci. Part A, 4, 1337, 1966.)... 

Figure 11.10 The setup of a library based on imine ligands. The general synthetic route is established by reacting a dicarbonyl backbone with an amine substituent. Libraries of different amines and dicarbonyls offer the perspective of obtaining sets of different ligands.

Only species Te 2- with short chains (n = 2-4) are present in polytelluride solutions [57]. Despite this fact many Zintl-type valence precise tellurium dianions of higher nuclearity have been isolated in the solid state in the presence of suitable counter cations. The three general synthetic routes to such polytelluride anions can be summarized with representative examples as follows ... 

The general synthetic route for the preparation of bridged phosphorus cavitand is outlined in Scheme 5. From the resorc[4]arene, bearing various substituents at the lower rim, the cyclization step, which leads to the formation of the four fused eight-membered rings, was performed with three-co-ordinated and four-coordinated phosphorus reagent to give respectively tet-ra-phosphite, tetra-phosphonite, and tetra-phosphate or tetra-phosphonate derivatives. 

A general synthetic route has been reported for a wide range of trialkyl phosphite complexes of noble metals, including the unstable white [RhLj] [L = P(OMe)3 or P(OEt)3]. Subsequent studies have shown that the former complex reacts with NOPFg in dichloromethane to give the hydride [RhH- P(OMe)3 5](PF6)2 in high yield. 

In this procedure, the ketone is first converted to its enol acetate by reaction with acetic anhydride in the presence of a proton acid. Since this enol acetylation is performed under equilibrating conditions, the more stable enol acetate (usually the more highly substituted isomer) is produced. Acetylation of this enol acetate, catalyzed by the Lewis acid boron trifluoride, usually leads to the formation of the enol acetate of a /3-diketone which is cleaved by boron trifluoride to form acetyl fluoride and the borofluoride complex of the /3-diketone. Thus, this procedure offers a convenient and general synthetic route... 

A general synthetic route to meso-ionic iV-acyl-l,3-thiazol-5-imines (108, R = Ph, = Me, R = Me or Ph, R = COPh) is provided by treatment of thiobenzamidoaminoacetonitriles, Ph-CS-NMe-CHR-CN, first with benzoyl chloride and then with aqueous alkali. Alternatively, the thiobenzamidoaminoacetonitriles and hydrogen chloride give the corresponding salts, which with benzoyl chloride and aqueous alkali give -acyl l,3-thiazol-5-imines Derivatives (108, R = SMe) have been obtained by treating 5-acylamino-4-thiazoline-2-thiones with methyl iodide and aqueous alkali. ... 

An elegant, general synthetic route to spirocarbocyclic systems (cf. Vol. 5, p. 55) involving regiospecific ring cleavage of appropriate tricyclic ketones [c/. (83)- (84)]... 

Consequently, only a handful M - Sb compounds have been synthesized and structurally characterized prior to 1995 [17,22]. Therefore, we and others investigated alternate pathways for the synthesis of M - Sb precursors and developed three general synthetic routes, to date. 

Scheme 16 General Synthetic Routes for Synthesis and On-Resin Cyclization...

The simple 1,2-dihydropyridine (63) cyclizes to the 2-azabicyclo[2.2.0]hexene (64) derivative upon irradiation (79JA6677). This reaction is the basis of a general synthetic route to dihydropyridines that are difficult to prepare by other means (Scheme 3). Dihydropyridines with more complicated substitution patterns, i.e. (66), undergo a photochemical rearrangement to valence isomers (68) and (69) (71T2957). The 1-azahexatriene (67) is believed to be an intermediate in this reaction (equation 21). 

There are numerous reactions reported in the literature that produce highly functionalized derivatives of the parent bicyclic compounds. Many of those reactions have been detailed in this chapter. For several of the bicyclic systems, general synthetic routes that lead to high product yields are unavailable. Many of the known synthetic routes lead to carbonyl derivatives of the ring systems. Within this chapter, these compounds have been treated in each section according to the ring substitution pattern. Likewise, syntheses of partially and fully reduced derivatives of the compounds are included with each parent compound. 

Scheme 1.1.26 General synthetic routes to a-phosphino alcohols.

A. Dondoni, M.-C. Scherrmann, A. Marra, and J.-L. Delcpine, A general synthetic route to anomeric a-azido and a-amino acids and formal synthesis of (+)-hidantocidin, J. Org. Chem. 59 7517 (1994). 

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