Reagents thionyl chloride

Alkyl halides are such useful starting materials for preparing other functional group types that chemists have developed several different methods for converting alcohols to alkyl halides Two methods based on the inorganic reagents thionyl chloride and phosphorus tnbromide bear special mention... 

These reactions have undergone extensive development and have proven to be general for the synthesis of these ring systems from any substituted o-diamine . The choice of the sulfur reagent, thionyl chloride, sulfur dioxide, sulfinylaniline or sulfur monochloride, depends upon the nature of substituents present. 

Synthesis of Acid Chlorides Acid chlorides (acyl chlorides) are synthesized from the corresponding carboxylic acids using a variety of reagents. Thionyl chloride (SOCl2) and oxalyl chloride (COCl)2 are the most convenient reagents because they produce only gaseous side products (Section 20-15). 

Elimination reactions of the 20-hydroxycholanic acid derivative (108) probably illustrate the differing character of the transition state, depending upon the reagent. Thionyl chloride in pyridine gave the 17(20)-enes (109 cis -I- trans, 80% total), as expected from thermodynamic control when a bimolecular elimination has considerable carbonium ion character ( l-like) in the transition state. The 20(22)-enes (110) cis + trans) were major products when phosphoryl... 

Dehydration of tert-alcohols.2 This reaction can be effected with BF3 etherate (1-3 equiv.) in CH2CI2 at 25°. Yields are usually higher than those obtained with the Burgess reagent, thionyl chloride/amine, or p-tolucncsulfonic acid. When dehydration could result in two different alkencs, the more thermodynamically stable alkenc predominates. Noepcntyl tert-alcohols result in mixtures of alkencs, some resulting from a carbocation rearrangement. 

Reagents thionyl chloride (pure if necessary, distilled with quinoline), benzene, p-toluidine, 5% HCl, 5% NaOH, ethanol. 

Reagent thionyl chloride, cone, ammonia, cone. H2SO4. 

Reagents thionyl chloride, 4n NaOH, 1% 1-naphthylamine in 2nHC1. 

Reagents thionyl chloride alcoholic solution of hydroxylamine hydrochloride 1—3% FeCl3 solution acetaldehyde 5% NaOH alcoholic HCl. 

Other than the LiBr/PPTS reagent, thionyl chloride (in the synthesis of (-l-)-danicalipm 14 A by Umezawa et al. ) and hydrochloric acid (in the syntheses of (-l-)-pericosine A 26" and blatteUastanosides A 55 and B 56 ) have also been used to promote the epoxide ring opening and to form the chlorohydrin stereoselec-tively (Scheme 42.16). 

The melting points of these esters are usually much lower than those of the corresponding 3 5 dinitrobenzoates their preparation, therefore, offers no advantages over the latter except for alcohols of high molecular weight and for polyhydroxy compounds. The reagent is, however, cheaper than 3 5 dinitrobenzoyl chloride it hydrolyses in the air so that it should either be stored under light petroleum or be prepared from the acid, when required, by the thionyl chloride or phosphorus pentachloride method. 

Thionyl chloride. This reagent (b.p. 76°) is generally used in excess of the theoretical quantity it cannot be employed for acetyd chloride (b.p. 52°) because of the difficulty of separation by fractional distillation. Excellent results are obtained, however, with butyrric acid and acids of higher molecular weight, for example ... 

Thionyl chloride and phosphorus tribromide are specialized reagents used to bring about particular functional group transformations For this reason we won t present the mechanisms by which they convert alcohols to alkyl halides but instead will limit our selves to those mechanisms that have broad applicability and enhance our knowledge of fundamental principles In those instances you will find that a mechanistic understand mg IS of great help m organizing the reaction types of organic chemistry... 

Thionyl chloride is a synthetic reagent used to convert alcohols to alkyl chlorides... 

Acid Chloride Formation. Monoacid chlorides of maleic and fumaric acid are not known. Treatment of maleic anhydride or maleic acid with various reagents such as phosgene [75-44-5] (qv), phthaloyl chloride [88-95-9] phosphoms pentachloride [10026-13-8] or thionyl chloride [7719-09-7] gives 5,5-dichloro-2(5JT)furanone [133565-92-1] (4) (26). Similar conditions convert fumaric acid to fumaryl chloride [627-63-4] (5) (26,27). NoncycHc maleyl chloride [22542-53-6] (6) forms in 11% yield at 220°C in the reaction of one mole of maleic anhydride with six moles of carbon tetrachloride [56-23-5] over an activated carbon [7440-44-4] catalyst (28). 

Benzisothiazoles are best prepared by oxidative cyclization of o-aminothiobenz-amides (see Section 4.17.9.1.1), reaction of o-toluidines with thionyl chloride (see Section 4.17.9.2.1) or by sulfuration of 2,1-benzisoxazoles (see Section 4.17.10.2). 1,2-Benzisothiazoles can also be prepared from o-disubstituted benzene compounds, cyclodehydration of o-mercaptobenzaldoximes or oxidative cyclization of p-mercaptobenzylamines (see Section 4.17.9.1.1) being the most convenient. Both series of benzo compounds are readily substituted at the 5- and 7-positions by electrophilic reagents. 

Jsomerides of Morphine and Codeine. When morphine is treated with thionyl chloride, phosphorus trichloride or tribromide, the alcoholic hydroxyl group is replaced by the halogen, forming a-chloromorphide and bromomorphide respectively. The former on treatment with concentrated hydrochloric acid is converted into /3-chloromorphide. Schopf and Hirsch have provided evidence that the two are structural isomerides. With the same reagents codeine yields a parallel set of compounds, viz., a- and -chlorocodides, and bromocodide. The chief characteristics of these products may be summarised thus —... 

One of the most widely used systems for dehydration is the combination of phosphorous oxychloride and pyridine. This reagent is apparently incompatible with the A" -3-keto system/ probably due to formation of a phosphorylated enol. It is, however, more selective than thionyl chloride-pyridine since 17a-alcohols are not dehydrated ... 

A -01efin formation can be avoided with thionyl chloride-pyridine by keeping the exposure brief and operating at low temperature in addition, the reagent may be used in the presence of a A" -3-ketone ... 

Another useful modification of this reagent is the reaction of CF3CCI3 with zinc and DMF in the presence of AICI3 [60, 63] (equation 53). The alcohol product can be treated subsequently with DAST, thionyl chloride, or phosphorus chlorides to afford the allyl substitution product regio- and stereoselectively [66] (equation 54). 

The use of azide reagents is also important for the synthesis of cyclic sulfur(VI)-nitrogen systems. The reaction of SOCI2 with sodium azide in acetonitrile at -35°C provides a convenient preparation of the trimeric sulfanuric chloride [NS(0)C1]3 (Eq. 2.16). " Thionyl azide, SO(N3)2 is generated by the heterogeneous reaction of thionyl chloride vapour with silver azide (Eq. 2.17). This thermally unstable gas was characterized in situ by photoelectron spectroscopy. The phenyl derivative of the six-membered ring [NS(0)Ph]3 can be prepared from lithium azide and PhS(0)Cl. ... 

The important reagent Mc3SiNSO is obtained by the reaction of thionyl chloride with tris(trimethylsilyl)amine at 70°C in the presence of AICI3 (Eq. 9.9). " It may also be prepared by the interaction of sulfur dioxide with HN(SiMc3)2. ... 

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