Pyridine thionyl chloride

Direct halogenation of sucrose has also been achieved using a combination of DMF—methanesulfonyl chloride (88), sulfuryl chloride—pyridine (89), carbon tetrachloride—triphenylphosphine—pyridine (90), and thionyl chloride—pyridine—1,1,2-trichloroethane (91). Treatment of sucrose with carbon tetrachloride—triphenylphosphine—pyridine at 70°C for 2 h gave 6,6 -dichloro-6,6 -dideoxysucrose in 92% yield. The greater reactivity of the 6 and 6 primary hydroxyl groups has been associated with a bulky halogenating complex formed from triphenylphosphine dihaUde ((CgH )2P=CX2) and pyridine (90). 

An economic synthesis of (3) has been patented (74,91). The process iavolves (/) synthesis of sucrose 6-acetate by way of sucrose 4,6-cychc orthoacetate (2), and (2) selective chlorination usiag thionyl chloride—pyridine—1,1,2-trichloroethane, followed by removal of the acetate group. 

Thionyl chloride/pyridine treatment of oximes (557) is believed not to proceed via an intermediate like (558) in the generation of 1,2-benzisoxazoles, but by a chloramine intermediate (Scheme 170). A similar reaction of an A-phenylhydroxamic acid generated a benzisoxazolinone via a proposed chloramine intermediate (Scheme 170) (77AJC1847). 

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 ... 

Trimethoxybenzoic acid Thionyl chloride Pyridine-2,6-dimethanol... 

In 1964, in order to compare the pharmacological behavior of both antipodes of thalidomide (1), Casini and Ferappi in Italy examined the preparation of (S)-thalidomide (1) from N-phthaloyl-L-glutamine (12) for the first time [85]. Namely, treatment of N-phthaloyl-L-glutamine (12) with one equivalent of thionyl chloride, pyridine, and then triethylamine in dichloromethane at - 30 °C gave (S)-thalidomide (1), [a]p° - 62° (Scheme 17). Although the reported method was straightforward, it was devoid of many synthetic details. 

The dehydration of an lijS-hydroxy-iia-methyl steroid (9) with thionyl chloride-pyridine [1247 is a curious case of the formation of an endocycHc olefin ii) which is distinctly... 

In this context, it is noteworthy that a 6a-acetoxy-5a-hydroxy- as well as a 6 -acetoxy-5a-hydroxy steroid is dehydrated by thionyl chloride/pyridine to give the corresponding 6-acetoxy-A4-olefin [128], despite the availability of a 6/ -hydrogen atom in the 6a-acetoxy derivative. This also can be rationalised in the terms used by Ingold, for a transition state of moderate cationic character would be further destabilised if one of the participating carbon atoms carries an electronegative substituent, irrespective of its configuration. The A -compound cannot therefore arise as a major product from such systems. 

A few related observations deserve comment. The presence of an ii-keto function completely inhibited solvolysis of the I2j0-sulphonates by its opposed inductive effect, but did not prevent the tosylhydrazone decomposition and rearrangement [1087. This may be a reflection of the exceptionally low activation energy for the decomposition of an aliphatic diazo-nium ion into a carbonium ion and molecular nitrogen (p. 316). Rather surprisingly, the Cps) cyanohydrin (15) undergoes similar rearrangement on dehydration with thionyl chloride/ pyridine [108,11 ]. 

An intramolecular version of this methodology was further applied to construction of amino sugars, such as the unnatural C-5 epimer of desosamine (399) (84JOC3243) and deoxyaminopentose (406) (85T1143). When ( , )-diene carbamate 393 was treated with thionyl chloride/pyridine between 0°C and room temperature, a single Diels-Alder adduct (395) was formed in 80% yield. The structure and stereochemistry of this dihydrothiazine oxide were... 

Dehydration see also Phosphoryl chloride-pyridine Thionyl chloride-pyridine). The dehydration of terpene alcohols with acidic reagents usually leads to several isomeric olefins, von RudlofP found that dehydration of terpene and sesquiterpene alcohols with neutral alumina (Woelm 1) to which 1-2% of pyridine or quinoline has been added gives a single or only a few products. The alcohol is heated under reflux at 200-230° for 1-6 hrs. with twice its weight of the treated alumina and the product isolated by steam distillation. 

I he 11/3-hydroxyl group to produce a 9,11-double bond (7), whereas on reaction with thionyl chloride-pyridine both the 11/8- and the 17a-hydroxyl groups were eliminated, giving (8). Thus SOCIj-Py is the more powerful reagent, but POCla-Py hits an advantage where selectivity is desired. 

This ring is formed when an -acyIaminoazole-2-carboxylic acid is heated with thionyl chloride-pyridine. Lower yields are recorded when DCC-THF is used. 

Prolonged heating of a cinnamic acid with thionyl chloride-pyridine is a useful synthesis of 3-chlorobenzo[6]thiophene-2-carbonyl chlorides. 

Substituted 5-vinyl-2,3-dihydro-1,4-dioxins (150), prepared by dehydration of allylic alcohols (142) with mesyl chloride-triethylamine or thionyl chloride-pyridine, undergo [4 -I- 2] cycloaddition reactions with various dienophiles to give the adducts (151). Exposure of (151), obtained by Diels-Alder reaction with dimethyl alkynedicarboxylate, to l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) followed by acidic hydrolysis affords the highly functionalized diesters (152) <88JOC5672>. 

Thionyl chloride/pyridine s. Pyridine/thionyl chloride SOCla/CaH N... 

When the epoxide (presumably the a-form, XXXIV) is reduced with lithium aluminum hydride in ether-benzene and the reaction product reacetylated with acetic anhydride-pyridine, there is formed an 0,0 -diacetyl-W-ethylhydroxydihydroveratramine (XL), which readily loses water in contact with thionyl chloride-pyridine to generate an 0,0 -diacetyl-iV-ethylveratramine (XLI). During this reduction there is also formed a product which on reacetylation proved to be 0,0 -diacetyl-iV-ethyldihydroxydihydroveratramine (XLII). Its structure is uncertain but it appears to be formed by hydrolytic rather than reductive cleavage of the epoxide ring (42). 

Under the mild conditions employed (eqs 3 and 4), racemi-zation of stereogenic centers, skeletal rearrangement, or byproduct formation, seen with other reagents such as thionyl chloride/ pyridine, are seldom observed. 

Thionyl chloride pyridine a-Acylimino- from a-acylamino-nitriles 505. CeHs-CH-CN... 

Thionyl chloride/pyridine Aromatization by allyl rearrangement... 

---