Allyl thiol

Synthesis of thiopheno[3,4-c isoxa2olide is shown in Eq. 4.4, in which the Michael addidon of allyl thiol to fi-nitro enones and subsequent nitnle oxide cyclizadon are involved. ... 

Potential precursors to stereoselective INOC and ISOC reactions (e.g., 195 and 196, respectively) have been prepared via stereoselective conjugate additions of several allylic alcohols (e.g., 194,X = 0) and an allylic thiol (e.g., 194,X = S) to a chiral (E)-nitro alkene (e. g., 193) that was derived from (P)-2,3-isopropylidene... 

In the context of diagenesis in recent anoxic sediments, reduced carotenoids, steroids, and hopanoids have been identified, and it has been suggested that reduction by sulhde, produced for example, by the reduction of sulfate could play an important part (Hebting et al. 2006). The partial reduction of carotenoids by sulfide has been observed as a result of the addition of sulfide to selected allylic double bonds, followed by reductive desulfurization. This is supported by the finding that the thiol in allylic thiols could be reductively removed by sulhde to produce unsaturated products from free-radical reactions (Hebting et al. 2003). 

Hebting Y, P Adam, P Albrecht (2003) Reductive desulfurization of allylic thiols by HS /HjS in water gives clue to chemical reactions widespread in natural environments. Org Lett 5 1571-1574. 

Characterization of the essential oils of onion and garlic was aided by the isolation of silver derivatives. The salts containing n-propanethiol and allyl thiol were both insoluble and could not be recrystallized.296... 

With (3), for instance, the ene reaction occurs at 0°C and has been applied to the synthesis of allylic thiols [515], through LiAlH4 reduction of the ene adducts. 

One solution is a [2,3] sigmatropic rearrangement of a sulfonium ylid. A stable allylic thiol reacts cleanly with an a-haloketone 64 to give a sulfide and hence the sulfonium salt after ethylation. Only a weak base is need to make the ylid 65 as this is also an enolate. Notice the regioselectivity here the alternative ylid would also be stabilised but only by an alkene. The [2,3] shift joins the allylic fragment to the enolate of the ketone and at the same time turns it inside out. This automatically produces the more difficult product 63 after desulfurisation with Raney nickel. We shall see alternative solutions to this problem later in the chapter.9... 

The Overman rearrangement has been extended to the synthesis of secondary allyl aryl ethers and allylic thiol carbamates, using a palladized oxazolinylcobaltocene-type complex (187)." The former reaction could very well be considered as an SN2 process. 

When Confaione was planning his synthesis of biotin (13), he chose intermediate (14) to supply all the carbon atoms as well as one nitrogen and the sulphur atom. A Michael disconnection gives allylic thiol (15) which can be made from allylic bromide (16) and hence from cycloheptene. 

Substitution reactions of attylic systems. An access to allylic thiols is based on substitution by MeCOSK with (dbaljPdj-dppb as catalyst. 2-Alkylidene-3-alkyl-l,4-benzodioxanes are readily formed in a reaction between catechols and propargylic carbonates. ... 

Thermal desorption of purged and trapped garlic breath was studied by GC/MS [53] in which allyl methyl sulfide, diallyl sulfide, diallyl disulfide, -cymene and D-limonene were found consistently in all subjects, however, allyl thiol was detected occasionally. Preliminary evidence suggest that stomach acid caused increased evolution of hydrogen sulfide, a potential breath odor compound, during digestion. 

Sigmatropic rearrangements of allyl sulphonium allyl ylides (75) provide the basis of a repetitive one-pot ring-expansion sequence" for 2-vinyl thiocyclic compounds (Scheme 50). A paper" and a section in a review article" have described the utilization of allyl thiol dianions and allyl sulphide anions in carbonyl group umpolung . 

Scheme 4.68). The possibility of using benzylic or allylic thiols as pronucleophiles is an important advantage of this methodology due to the easier removal of the benzyl or allyl moiety from the S atom, and therefore allowing the easy liberation of the latent mercapto functionality, if required. The only drawback associated to this methodology is the fact that a three-fold excess of the thiol reagent had to be employed in order to reach to full conversion. 

Hydroxy-terminated polymers prepared in this manner were used to build more complex macromolecular architectures such as graft copolymers [50] or block copolymers [51]. Using a 1,3-dithiepine instead of a 1,3-dioxepine as sacrificial monomer, allylic thiol polymer end groups could be obtained [52]. The poly(l,3-dithiepine) block was cleaved (sacrificed) under hydrogenation conditions using Raney-Nickel. 

A similar Nicolas-Pauson-Khand combination was used in a synthesis of the ketone analogue of biotin 7.98, required for biochemical studies (Scheme 7.25). In this case, the Nicholas reaction was intermolecular, between allyl thiol as the nucleophile and carbocation 7.94 generated from alcohol 7.93. The Pauson-Khand reaction was then between the dicobalt complexed alkyne 7.95 and the double bond from the thiol moiety. The Pauson-Khand reaction proceeded with no stereoselectivity, and the diastereoisomers had to be chromatographically separated at a later stage. The synthesis was completed by reduction of the alkene of cyclopentenone 7.96, without using palladium-catalysed hydrogenation due to the sulfide moiety, and ester hydrolysis. 

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