37676-91-8Relevant academic research and scientific papers
Synthesis and polymerization of methyl 3-methylcyclobutene-1-carboxylate
Kitayama, Tatsuki,Kawauchi, Takehiro,Ueda, Nori,Kniep, Carina S.,Shin, Won Suk,Padias, Anne B.,Hall Jr.
, p. 1591 - 1598 (2002)
A new icyclobutene monomer, methyl 3-methylcyclobutene-1-carboxylate (MMCB), has been synthesized and polymerized by radical and anionic initiators. The synthesis started from a [2 + 2] cycloaddition of N-(1-propenyl)piperidine to methyl acrylate, followed by methylation and treatment with base to yield the monomer. Free radical polymerization of MMCB led to low yields of low molecular weight polymers, probably due to chain transfer at the allytic hydrogen. However, p-methoxystyrene, styrene and methyl methacrylate gave high molecular weight copolymers with MMCB in high yields. Anionic homopolymerization with tert-butyllithium (t-BuLi), t-BuLi/bis(2,6-di-tert-butylphenoxy)ethylaluminum, lithium bis(trimethylsilyl)amide, and potassium bis(trimethylsilyl)amide in toluene at 0 and -78°C proceeded smoothly and gave polymers in high yields. NMR and IR analyses of the polymers suggested that the polymerization proceeds via addition mechanism without ring-opening. Thermal properties of the polymers are also described briefly. In contrast to MMCB, methyl 3,3-dimethylcyclobutene-1-carboxylate MDCB did not polymerize due to excessive steric hindrance.
Ring-closing metathesis of allylsilanes as a flexible strategy toward cyclic terpenes. Short syntheses of teucladiol, isoteucladiol, poitediol, and dactylol and an attempted synthesis of caryophyllene
Dowling, Matthew S.,Vanderwal, Christopher D.
experimental part, p. 6908 - 6922 (2010/11/24)
The development of a strategy consisting of allylsilane ring-closing metathesis and subsequent SE′ electrophilic desilylation (allylsilane RCM/SE′) to construct exo-methylidenecycloalkanes is described. Its utility is documented in short syntheses of teucladiol and poitediol. A key transformation in the synthesis of teucladiol is an aldol addition that establishes three stereochemical relationships in one step with ≥10:1 diastereoselectivity and provides a fascinating example of double stereodifferentiation/kinetic resolution with racemic reaction partners in the context of natural product synthesis. The synthesis of (±)-teucladiol required five steps from cyclopentenone and proceeded in 28% overall yield; adaptation of this route to an enantioselective synthesis of (-)-teucladiol enabled the determination of the absolute configuration of this terpene natural product. The use of fluoride-mediated conditions in the final desilylation step preserves the location of the alkene, delivering the natural product (±)-isoteucladiol (five steps and 21% yield from cyclopentenone). The synthesis of poitediol showcases the power of RCM for constructing eight-membered rings and features a highly diastereoselective epoxidation/fluoride-mediated fragmentation sequence for installing the exo-methylidene group with an adjacent hydroxyl-bearing stereocenter. The synthesis of (±)-poitediol required seven steps and proceeded in 18% overall yield. Again, fluoride-mediated desilylation of a late-stage intermediate (with retention of double-bond location) delivered the natural product (±)-dactylol (seven steps and 24% yield). Efforts directed toward incorporating the RCM/SE′ sequence into a synthesis of caryophyllene are also disclosed. While ultimately unsuccessful, these efforts resulted in the identification of a novel metal alkylidene-promoted deallylation reaction of terminal 1,4-dienes. A possible mechanism for this unexpected deallylation reaction of 1,4-dienes is provided.
THE STEREOCHEMISTRY OF THE INTRAMOLECULAR ELECTROPHILIC ATTACK OF AN ALDEHYDE ON A CARBON-TIN BOND
Fleming, Ian,Rowley, Michael
, p. 3181 - 3198 (2007/10/02)
The cyclopentane-forming reaction (20-43) of (4RS,5SR)-2,2,4-trimethyl-5-trimetstannylhexanal takes place with retention of configuration at the carbon atom undergoing electrophilic substitution, in contrast to similar cyclopropane-forming reactions (e.g. 47-48), which take place with inversion of configuration.The hydride transfer (24-45) of the 4RS,5RS diastereoisomeric hexanal takes place from a conformation with hydride anti to the stannyl group.In the case of reacions which might have formed four-membered rings, fragmentation takes place (16-28 and 17-30).The presence of a phenyl ring on the carbon carrying the stannyl group interferes with the reactions designed to test the stereochemistry of the SE2 reaction, diverting the reaction to the formation of tetralins (10-26 and 34-38) or benzcycloheptenes (34-37).
