Stephen reaction

From nitriles by treatment with anhydrous Stannous chloride dissolved in ether saturated with hydrogen chloride the resulting crystaUine aldimine stannichloride, [(RCH=NHj)2] SnCl, or (RCH=NH,HCl)2SnCl4, is hydrolysed by warm water, and the aldehyde is isolated by distillation with steam or by extraction with a solvent (Stephen reaction), for example, for R = CH3(CH2)4, i.e., n-amyl ... 

Stephen reaction Stobbe condensation UUmann reaction Willgerodt reaction. ... 

The reduction of the nitrile groups and subsequent Stephen reaction followed by... 

Snieckus and his group members [104] used the known domino Sonogashira/ Castro-Stephens reaction [105, 106] for the synthesis of the natural product pli-cadin (6/1-209), this having been isolated from Psorelia plicata in 1991 [107]. In this synthesis, Pd°-catalyzed reaction of the alkyne 6/1-210 and the iodobenzene derivative 6/1-211 in the presence of Cul led to the furan 6/1-212, which was transformed into 6/1-209 via 6/1-213 (Scheme 6/1.54). There are some discrepancies of the physical data of the natural and the synthetic product thus, it might be possible that the natural product has a different structure. It should also be mentioned that the... 

Bis-acetylene synthesis from alkynyl halides and alkynyl copper reagents. Cf. Castro-Stephens reaction. 

Pd/Cu-catalyzed cross-coupling of organohalides with terminal alkynes. Cf. Cadiot-Chodkiewicz coupling and Castro-Stephens reaction. The Castro-Stephens coupling uses stoichiometric copper, whereas the Sonogashira variant uses catalytic palladium and copper. 

In a laboratory-scale synthesis of rofecoxib (2), a ruthenium-catalyzed lactonization of diarylacetylene 19 gave rise to 2 regioselectively (Scheme 4)." Diarylacetylene 19, on the other hand, was prepared by utilizing a Castro-Stephens reaction of p-iodophenyl methyl sulfone and copper(I) phenylacetylene in pyridine under reflux. In another case, Fallis and coworkers synthesized butenolide in 2 using a magnesium-mediated carbometallation reaction. Therefore, treatment of... 

Although the authors call this reaction a Castro-Stephens reaction, they point out that it is really a Linstrumelle modification of the Sonogashira protocol. 

Stannous chloride, anhydrous. 197 see also Stephen reaction Starch, 458 ... 

The reduction of a nitrile is achieved with anhydrous tin(n) chloride dissolved in ether or ethyl acetate saturated with dry hydrogen chloride (the Stephen reaction). The resulting aldimine hydrochloride (probably in the form of a complex with tin(iv) chloride) is then hydrolysed with warm water. 

The most widely used Pd-catalyzed alkynylation for the synthesis of alkynes, the Sono-gashira reaction, is the hybrid of alkyne version of the Heck reaction and Cu-promoted Castro-Stephens reaction (Scheme 5.20). 

Castro-Stephens reaction Heck alkynylation Sonogashira alkynylating... 

The synthesis of aldehydes by the Sommclet reaction, the Rosenmund reduction and the Stephens reaction all involve the conversion of a group already present in the molecule. The Rosenmund reduction (Scheme 6.7) is the catalytic hydrogenation of a benzoyl chloride in the presence of a catalyst poison, quinoline/sulfur, which prevents over-reduction to the alcohol. In the Stephens reaction (Scheme 6.7), a nitrile group is reduced by tin(II) chloride and hydrochloric acid to an imine salt, which is then hydrolysed. 

In most cases, the crude imino chloride is treated directly by adding it to a solution of stannous chloride saturated with dry hydrogen chloride the aldehyde is then liberated by steam distillation. The procedure is illustrated by the synthesis of o-tolualdehyde (70%). Imino chlorides have also been prepared by treatment of ketoximes with phosphorus penta-chloride, viz., RR C NOH — RCC1=NR, in preparations of benzalde-hyde and p-chlorobenzaldehyde (70-85%). As in the Stephen reaction (method 164), groups ortho to the imino chloride group hinder the reaction. 

The Castro-Stephens Reaction Preparation of Disubstituted Alkynes and Enynes... 

The Castro-Stephens reaction entails coupling of alkynylcopper(I) reagents with aryl or heteroaromatic halides in refluxing pyridine to furnish arylacetylenes. The cuprous alkynylides are prepared by adding the 1-alkynes to an aqueous ammonia solution of cuprous iodide. Since dry copper alkynylides have the tendency to explode, they must be handled with great care and should only be used in a slightly damp state. ... 

During the total synthesis of epothilone B, J.D. White et al. used the modified Castro-Stephens reaction instead of a Wittig reaction for the coupling of two important subunits (A B) to avoid strongly basic conditions. 

The ether-soluble anhydrous reagent is used in the preparation of )3-naphthaldehyde by the Stephen reaction and of o-tolualdehyde by the Sonn-Miiller reaction. A... 

The procedure outlined above describes the selective, retentive, p-coupling of (Z)-2,3-dibromopropenoic acid ethyl ester with (trimethylsilyl)acetylene employing the palladium-modified version of the Castro-Stephens reaction.4 5 The dibromide starting material is readily available by bromination of ethyl propiolate (Procedure A), as described by Trippett and Hall.2 The coupling product has been shown to be a versatile precursor for the synthesis of variously substituted enynes and enediynes. For example, a second acetylene may be introduced into the a-position under modified coupling conditions. Alternatively, reduction of the ester with diisobutylaluminum hydride and protection of the resultant alcohol with tert-butyldiphenylsilyl chloride affords a vinyl bromide that can be metalated and trapped with various electrophiles. These procedures have been used on the gram and multigram scale.5... 

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