Addition of Alkyl Radicals to Alkynes: Distinction between Radical and Ionic Nucleophiles

✍ Scribed by Prof. Dr. Bernd Giese; Dr. Stephen Lachhein

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 225 KB
• Volume: 21
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.198207681

✦ Synopsis

Me = Et > i-Pr & t-Bu"]. I-tert-Butoxy-2,7-octadiene, which was not obtained with conventional catalysts, is also formed. Higher telomers are formed in all cases except with t-BuOH. The presence of large amounts of phenoxy-C,2-derivatives may reflect an alteration in the reaction mechanism.

The reaction presumably proceeds via condensation of C8-units, since almost only C8,,-products are formed. Indeed, I -methoxy-2,7-octadiene 2 is converted inter alia into the ether 5. The occurrence of two or even three vacant coordination sites may be a prerequisite for the formation of such higher telomers.

Procedure

Solution of l a : A mixture of Pd,(dba)3.CHC1,[41 (130 mg, 0.125 mmol) and [(CH2=C(CH,)CH20)P(NMe2)3]ePF~[s1 (95 mg, 0.25 mmol) is placed in a 50 mL Schlenk tube and degassed by three vacuum-argon atmosphere cycles. Toluene (10 mL) is then added and the reaction mixture stirred under argon for 120 min.

Catalytic reaction: The pale yellow solution is filtered through Celite in order to remove traces of metallic palladium and then transferred via a syringe into a glass-lined 100 mL stainless steel autoclave. Methanol (3 mL, 75 mmol) and butadiene (16.2 g, 300 mmol) are then added. The autoclave is stirred magnetically and heated to 80 "C for 20 h ; it is then cooled down and the excess butadiene is vented through a cold trap. The conversion is 94%. The products are analyzed by GC with dodecane and eicosane as internal standards.

All reactions are carried out under argon.