“…The cleavage of allylic-, propargylic and vinylic ethers by [(C 5 Me 5 ) 2 Sm(THF) n ] was investigated via NMR. 169–171 Allylic ethers are cleaved by [(C 5 Me 5 ) 2 Sm(THF) 2 ], as evidenced by various examples, e.g. the reaction of desolvated [(C 5 Me 5 ) 2 Sm] and allyl benzyl ether gave the allyl compound [(C 5 Me 5 ) 2 Sm(C 3 H 5 )] and the alkoxide compound [(C 5 Me 5 ) 2 Sm(OBn)] (Scheme 51).…”
Section: Reactivity As a Reducing Agentmentioning
confidence: 99%
“…Scheme 51 Reactivity of [(C 5 Me 5 ) 2 Sm(THF) 2 ] towards allylic ethers to yield allyl complexes 169. …”
“…The cleavage of allylic-, propargylic and vinylic ethers by [(C 5 Me 5 ) 2 Sm(THF) n ] was investigated via NMR. 169–171 Allylic ethers are cleaved by [(C 5 Me 5 ) 2 Sm(THF) 2 ], as evidenced by various examples, e.g. the reaction of desolvated [(C 5 Me 5 ) 2 Sm] and allyl benzyl ether gave the allyl compound [(C 5 Me 5 ) 2 Sm(C 3 H 5 )] and the alkoxide compound [(C 5 Me 5 ) 2 Sm(OBn)] (Scheme 51).…”
Section: Reactivity As a Reducing Agentmentioning
confidence: 99%
“…Scheme 51 Reactivity of [(C 5 Me 5 ) 2 Sm(THF) 2 ] towards allylic ethers to yield allyl complexes 169. …”
“…In previous papers, we have reported a selective C−O bond cleavage of allylic, propargylic, and vinylic ethers with Cp* 2 Sm(thf) n leading to allyl-, allenyl-, and vinylsamarium complexes, respectively. Moreover, it has been found that allenylsamarium complexes thus generated exhibit a completely opposite regiochemistry in the reaction with electrophiles to the corresponding complexes prepared by transmetalation, as shown in Scheme . , 1 …”
The C−O bond of allylic benzyl ethers was selectively cleaved
with Cp*2Sm(thf)
n
to give
allylic
samarium complexes in good yields. Facility of their bond fission
has been found to be comparable
to that of the corresponding propargylic ethers intermolecularly, but
lower intramolecularly. Regio-
and stereochemistry on the electrophilic trapping of the allylic
complexes thus generated remarkably
depended on the nature of the electrophiles. They reacted with
carbonyl compounds exclusively
from the most substituted terminus of the allylic moieties to yield
blanched homoallylic alcohols
with anti diasteroselectivity. On the other hand, trapping with
silyl chlorides produced linear allylic
silanes. Here, a plausible mechanism to account for the difference
is proposed.
“…From a synthetic point of view, these C−O bond cleavage reactions can serve as a convenient method for generation of the useful lanthanide reagents. We reported previously the facile generation of allylic and allenic samariums from benzyl allyl ethers and benzyl propargyl ethers, respectively, by the reaction with (C 5 Me 5 ) 2 Sm(thf) n . In continuing work, we studied regioselectivity on the reductive cleavage of alkyl vinyl ethers, i.e.…”
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