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The synthesis of 4‐ 2 H‐α‐farnesene and 1‐ 2 H‐α‐farnesene
Author(s) -
Fielder Simon,
Rowan Daryl D.,
Reay Peter F.
Publication year - 1993
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580331011
Subject(s) - chemistry , deprotonation , deuterium , thermal decomposition , medicinal chemistry , alkylation , lithium (medication) , quenching (fluorescence) , double bond , organic chemistry , catalysis , ion , medicine , physics , quantum mechanics , fluorescence , endocrinology
α‐Farnesene deuterated at C1 or C4 was synthesised by regiospecific deuteration of 2‐geranyl‐3‐methylsulpholene (2). Treatment of (2) with butyl lithium in dimethylpropenylurea (DMPU) mediated THF resulted in deprotonation at C2. Quenching with D 2 O/CH 3 CO 2 D gave a mixture of deuterated sulpholenes (43‐68%), predominantly 2‐ 2 H‐2‐geranyl‐3‐methylsulpholene (5), together with bond migrated product (25‐49%). Thermal elimination of sulphur dioxide gave 4‐ 2 H‐α‐farnesene (6)(85%) but with low deuterium incorporation (60%) and poor regiospecificity. Treatment of (2) with butyl lithium in TMEDA mediated THF resulted in deprotonation at C5 with minimal bond migration (1%). Quenching with D 2 O/CH 3 CO 2 D yielded 5‐ 2 H‐2‐geranyl‐3‐methylsulpholene (18)(75%) which on thermolysis gave 1‐ 2 H‐α‐farnesene (19)(86%) with high regiospecificity and improved deuteration (85%). Some mechanistic aspects of the alkylation of 3‐methylsulpholenes are discussed.