Furfuryl halides

Furfuryl mercaptan cannot be prepared according to the classical method using furfuryl chloride and potassium sulfide.2 It has been prepared by reduction of 2-furfuryl disulfide, obtained from furfural and ammonium hydrosulfide.3 The mercaptan has also been obtained in 33% yield 2 by the reaction of furfuryl chloride with thiourea and subsequent decomposition of the intermediate S-2-furfurylisothiourea according to the general method described in Organic Syntheses.4 In the present method, which has been published previously, the use of the very unstable and difficultly available furfuryl halides is avoided.6... 

The furfuryl halides [cf. 385 (Z = 0)] are exceedingly reactive they are usually not isolated but are used in solution as intermediates because of their instability. The halogen can be replaced directly by amino or alkoxy groups, but with potassium cyanide the SN product 367 (see Section 3.3.3.3.3) is also formed. 2,5-bis(chloromethyl)furan is a precursor for highly conductive high-molecular-weight poly(2,5-furylene vinylene). 

The nucleophilic displacement of halide from furfuryl halides often produces mixtures of products resulting from straightforward displacement on the one hand, and displacement with nucleophilic addition to C-5 on the other the second mode proceeds through a non-aromatic intermediate, which then isomerises to aromatic product. 

Bromomethyl-5-methylthiophene gives normal displacement products with amines but it is isomerized on attempted reaction with copper(I) cyanide (Scheme 59) 48MI30200. Whereas 2-hydroxymethylthiophene reacts normally with hydrogen halides to give 2-halomethylthiophenes, reaction of 2-hydroxymethylfuran (2-furfuryl alcohol) with hydrochloric acid results in formation of laevulinic acid (151). 2-Furfuryl alcohol derivatives are... 

Furfuryl chloride can undergo substitution by both SN2 and SN1 mechanisms. Since it is a 1° alkyl halide, we expect SN2 but not SN1 reactions. Draw a mechanism for the SN1 reaction shown below, with careful attention to the structure of the intermediate. How can this primary halide undergo SN1 reactions Why is there no competition with E2 or El mechanisms ... 

Among the various derivatives of biomass, furan compounds obtained from furfural are important (200 000 t year ). A new family of furan diethers has been obtained by alkylation of 2,5-furandimethanol or furfuryl alcohol under the action of microwave irradiation with PTC solvent-free conditions (Scheme 10.79) [154]. Reaction times were improved by use of microwave irradiation, and the same conditions were extrapolated to the synthesis of a series of new furan diethers by alkylation of furfuryl alcohol by dihalides. 1,4-Diketones substituted by furans or thiophenes were synthesized by conjugate addition of aldehydes to a,j8-unsaturated ketones by irradiation without solvent in the presence of thiazolium halides and DBU adsorbed on alumina [155]. 

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