2-Furyllithium preparation

Very many naturally occurring 3-alkyl- or 3-acylfurans are now routinely synthesized by preparing a substrate for treatment with 3-furyllithium, itself made from 3-bromofuran according to Fukuyama, Tokoroyama, and Kubota, who used it to obtain pyroangensolide and fraxinellone.212 Equally, 2-lithiofuran is used for such natural products as the acetylenic furans from Alphonsea ventricosa213 and other compounds.214 For the synthesis of the sesquiterpenoid sponge-metabolite pleraplysillin-2 78, the lithiofuran 79 and therefore the bromofuran 80 was needed to secure the orientation a suitable preparation was devised for 80.215... 

We owe to Kato and his colleagues a considerable advance in furan copper reagents. They have demonstrated the formation of the lithium di(3-furyl) cuprate species 87 which is highly reactive and possesses hard properties that suit it to reaction at hard centers, mainly carbonyl carbon.223 The reagent is easily prepared in situ from 3-furyllithium and Cu2I2. Simple copper derivatives do not react with ketones, but this cuprate reacts well and quantitatively with acid chlorides. It also reacts well with some epoxides (oxirans). Moreover, there is another form prepared in the presence of... 

Furan-2-boronic acid (89) and furan-3-boronic acid are readily prepared by interaction of the furyllithium with methyl borate (MeO)3B followed by acid hydrolysis.233 234 Like most boronic acids they owe their acidity more to coordination with a water molecule than to simple proton transfer they... 

As shown in Scheme 15, 4-substituted 4-hydroxy-2,6-dimethyl-4//-pyrans 324 and 325 were obtained by reaction of 4-pyrone 322 with BuLi320 or substituted furyllithium reagents,321 respectively. 4,4-Disubstituted 2,6-dimethyl-4//-pyrans 326 were prepared by the reaction of a threefold excess of the corresponding Grignard reagents RMgX with 4-pyrone 322.3 1,316... 

Older methods of preparing furanthiols and their derivatives have been overshadowed by lithiation techniques in which the metallated furan is treated with sulfur and alkylated to give the desired alkylthiofurans.198,199 Phosphoryl thioesters are obtained in the same way, as are their selenium equivalents.200 2-Furyllithium affords lithium furan-2-selenite when treated with selenium dioxide.201... 

Retrosynthetic considerations suggested that the obvious inducement for us was the opportunity to transform the known optically pure ketone 82 [49] into 83 in advance of an anionic Cope rearrangement (Scheme XI) [50]. Although 1,2-addition of the cerate prepared from 3-furyllithium proceeded with appropriately high facial selectivity, subsequent isomerization of the potassium salt of 83... 

Solutions of 0.06 mol of furyl- or thienyllithium in equal amounts of THF and hexane are prepared as described in the preceding experiments. The solutions are cooled to 0 °C and 0.05 mol (8.6 g) of benzyl bromide is added in one portion. After a few minutes the temperature rises to over 20 °C. Occasional cooling (with a dry ice acetone bath) serves to keep the temperature between 20 and 30 °C. Comparison of the reaction of benzyl bromide with furyllithium with that of thienyllithium under similar conditions shows that the latter reacts faster. After keeping the solutions for... 

Reaction of furyllithium (60) with L-threonine derived lithium salt 61 afforded the expected ketone 62 in 30% yield. Reduction of 62, using lithium aluminium hydride, gave two alcohols (63 and 64) in a 3 1 ratio. In both carbinols (63 and 64) the oxazoline ring was opened by acid hydrolysis to give the N-benzoyl derivatives 65 and 66, respectively. Alcohol 66 can be used in the synthesis of lincosamine enantiomer, but unfortunately this approach has limited preparative value because of the low yield obtained in the condensation step and, on the other hand, opposite diasteroselectivity obtained in the reduction reaction. 

D-mannose derivatives, (see Vol. 22, p. 161).29 a new stereoselective total synthesis of (+)-KDO (27) proceeds via the adduct (28) from 2-furyllithium and isopropylidene-D-glyceraldehyde (Scheme 10).3O A full account has been given of a KDO synthesis by free-radical extension of a mannose derivative at C-6 (see Vol. 22, p. 162),31 and there has been a further report on the preparation of 3-deoxy-L-5(ulo-2-octulosonic acid [the C-7 epimer of (27)] by similar methods to those previously used (see Vol. 22, p. 162).32... 

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