Halides, alkyl from aldehydes

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

One of the first papers was published by Corey on the use of bis(methylthio)allyllithium (1 Scheme 14) for the synthesis of a,p-unsaturated aldehydes from alkyl halides. The generation of the carbanion as the lithio derivative was readily accomplished by a simple three-step sequence from epichlorohydrin. 

The lithiated oxathiolan dioxide (19) has been used as a carbonyl anion equivalent to give high yields of aldehydes from alkyl halides and acyloins from cyclic ketones.The /8-acyl anion equivalent (20 X = Li), which can be prepared from the stannylated diene (20 X = SnRs) by metal exchange, reacts with a variety of electrophiles (E ) to give dienes (20 X = E) in good to excellent yields.The thiophosphate (21) gives a,/3-unsaturated esters in 48—68% yield... 

The use of iron carbonyl derivatives in organic synthesis is often limited by the difficulty of separation of the iron complexes from the desired product at the end of the reaction. In the synthesis of aldehydes from alkyl halides using tetra-carbonylhydridoferrate, [HFe(CO)4] , this problem has been overcome by attaching the iron complex to an ion-exchange resin [equation (9)]. The resin converts alkyl halides into the homologous aldehyde in over 90% yield, and at the end of the reaction the iron complex is retained on the polymer. Allyl chlorides fail to react, and secondary alkyl halides undergo elimination. 

Dyestuff intermediate, vulcanising accelerator. Reagent used in Krohnke synthesis of aldehydes from alkyl halides. Used as 0.025% soln. in EtOH for photometric detn. of Pd, Pt, Rh, Ru, Os, Ir. Green plates (Et20). Sol. EtOH, Et20 si. sol. H2O. Mp 92.5-93.5° (85-87°). p. 9.71 (25°). Steam-volatile. 

In all the desulphonylation reactions discussed in Sections III.B and III.C the sulphur is lost from the starting sulphone and is reduced in the process simultaneously, the former carbon-sulphur bond is either reduced to a C—H bond or is converted into a C=C bond. The reactions described in this section have the common thread that the sulphur atom is lost with reduction at sulphur, but the carbon atom is converted directly into a carbonyl group. Formally, these reactions offer a route from alkyl halides to aldehydes or ketones. 

Organometallic compounds or carbanions undergo a number of reactions in which the carbanion or carbanion-like moiety of the organometallic compound acts as a nucleophilic displacing agent. Examples are the formation of hydrocarbons from alkyl halides, alkyl halides from halogens, and ketones from acid chlorides or esters. The latter two reactions are closely related to the base-catalyzed condensations and are perhaps additions as well as displacement reactions. Related addition reactions are the carbonation of organometallic compounds and the addition to ketones or aldehydes. 

Peptidomimetics in which one amide bond is replaced by a phosphinic acid (R-P(0H)(=0)-R phosphinic peptides ) are of interest as potential protease inhibitors [17-19]. These compounds have been prepared either from orthogonally protected phosphorus-containing monomers [17,18,20], or by forming the phosphorus-containing fragments on solid phase, as sketched in Figure 11.4 [19,21], Phosphinic acids have been prepared on solid phase mainly by reaction of carbon electrophiles with monoalkylphosphinates. As carbon electrophiles, acrylates, aldehydes, reactive alkyl halides, or a, 3-unsaturated ketones can be used. 

The protected methyl glycoside 3 is converted to the corresponding aldehyde by Swern oxidation using oxalyl chloride activated DMSO. Further reaction with triethyl phosphonoacetate and sodium hydride -known as the Horner-Wadsworth-Emmons reaction - provides selectively the trans et /Tun saturated ester 4 in 72 % yield. This valuable alternative to the Wittig olefination protocol uses phosphonate esters as substrates which are readily available from alkyl halides and trialkyl phosphites via the Arbuzov rearrangement.9 co2Et Reaction of the phosphonate with a suitable base gives the... 

Identification of naturally occurring organic sulfur compounds (OSC) is possible by co-chromatography (on capillary GC) and comparison of mass spectra (by GC-MS) with synthesized standards. Methods of preparation of various thiophenes (e.g. from suitable thiophene precursors and coupling with either the appropriate carboxylic acid, aldehyde or alkyl halide) will be outlined in addition to some of their spectral properties (NMR, IR,... 

Functional Group Transformations Functional group transformations help us in the conversion of a functional group to an aldehyde or a ketone without affecting the carbon skeleton of the molecule. Aldehydes can be synthesised by the oxidation of primary alcohols, or by the reduction of esters, acid chlorides, or nitriles. Since nitriles can be obtained from alkyl halides, this a way of adding an aldehyde unit (CHO) to an alkyl halide ... 

C-(w-propyl)-N-phenylnitrone to N-phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami-noacetone hydrochloride, 45,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47,1 /8-chloro-og3-unsaturated, from ketones and dimethylformamide-phosphorus oxychloride, 46, 20 from alkyl halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodiimide, and pyridinium trifluoroacetate, 47, 27 Alkylation, of 2-carbomethoxycyclo-pentanone with benzyl chloride, 45, 7... 

Alkanes, RH (Sec. 7.7) (Sec. 10.7) (Sec. 10.8) (Sec. 19.9) from alkenes by catalytic hydrogenation from alkyl halides by protonolysis of Grignard reagents from alkyl halides by coupling with Gilman reagents from ketones and aldehydes by Wolff-Kishner reaction... 

Silver salts are also utilized to perform nucleophilic additions to disulfide bonds to yield sulfenamides (146). If alkyl halides are treated with stoichiometric AgBF4 in dimethyl sulfoxide solvent (DMSO, solvent), the corresponding aldehydes/ ketones will form in good yields. This reaction is an alternative to the well-known Swern oxidation (147). In addition, silver can drive the formation of dialkylper-oxonium ions from alkyl halides, which then oxidizes sulfoxides or sulfides (148,149). In the presence of AgN03, sulfides can be oxidized into a-chloro sulfoxides by SO2CI2 (Fig. 36) (150). 

Dipotassium Iron tetracartxsnyl in the synthesis of aldehydes and ketones from alkyl halides. 

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