Alcohols from cyclopropanes

Other by-products include acetone, carbonaceous material, and polymers of propylene. Minor contaminants arise from impurities in the feed. Ethylene and butylenes can form traces of ethyl alcohol and 2-butanol. Small amounts of / -propyl alcohol carried through into the refined isopropyl alcohol can originate from cyclopropane [75-19-4] in the propylene feed. Acetone, an oxidation product, also forms from thermal decomposition of the intermediate sulfate esters, eg. 

The Tafel rearrangement only occurs in acid medium. Simultaneous reduction of both carbonyl groups leads to interaction and formation of a cyclopropane. Acid catalysed cyclopropane ring opening follows to yield an a-diketone 28 which undergoes the electrochemical Clemmensen reduction step to the hydrocarbon. Side products include the two monoketones derived by partial deoxygenation of the a-diketone and the secondary alcohols from reduction of these raonoketones. Separate experiments show that the a-diketone 28 can be reduced to the hydrocarbon. 

The tartaric acid scaffold also led to the design of one of the most effective and general methods to generate enantiomerically enriched substituted cyclopropyhnethanol derivatives. Indeed, the chiral dioxaborolane ligand 19, prepared from tetramethyltartramide and butylboronic acid, is a superb chiral additive in allylic alcohol-directed cyclopropanation reactions (equation 83) . The best procedure requires the use of the soluble bis(iodomethyl)zinc DME complex . The reaction affords high yields and enantiomeric... 

Some of the evidence for this comes from a reaction that not only throws light on to the mechanism of Simmons-Smith cyclopropanations, but makes them of even greater value in synthesis. When an allylic alcohol is cyclopropanated, the new methylene group adds stereoselectively to the same face of the double bond as the alcohol group. 

In this context, zirconium chemistry could open up new prospects for developing deoxygenative approaches to cyclopropanes. The Zr-assisted variant of the Kulinkovich reaction has been reported (Scheme 4, Eq. 1) [10]. Cyclopropanols were also formed, as by-products in addition to homoallylic alcohols, from aliphatic acid chlorides (Eq. 2) [ 10]. The conversion of acid chlorides (and also esters in several cases) into the corresponding homoallylic alcohols... 

Figures 6.21 and 6.22 summarize our synthesis of plakoside A (161) and its diastereomer 161 in 2001.25,26 As I will describe later in this section, plakoside A was proved to be 161, not 161. Plakoside A (161) can be prepared from the three building blocks, A, B and C. D-Galactose will be the starting material for A, while B and C can be synthesized from cyclopropane alcohol D and L-serine or D-glutamic acid,...

The consistency of the high levels of enantiocontrol accessible in these diazoester cyclizations is underpinned by their growing applications in enantiose-lective synthesis of bioactive molecules containing cyclopropane units. Notable examples include the preparation of multifunctional cyclopropanes as peptide isosteres for renin inhibitors (Scheme 4) [42] presqualene alcohol from farnesyl diazoacetate (Scheme 5) [43] the GABA analogue 3-azabicyclo[3.1.0]hexan-2-one from N-allyldiazoacetamide, Eq. (26) [23] and precursors of lR,3S)-cis-chrysanthemic acid and the pheromone, E-(-)-dictyopterene C (Scheme 6) [44, 45],... 

Matsuo, A., H. Nozaki, M. Nakayama, Y. Kushi, S. Hayashi, N. Kamijo, V. Benesova, and V. Herout X-Ray Crystal and Molecular Structure of the /7-Bromobenzoate of (— )-Myliol, a Novel Tetracyclic Sesquiterpene Alcohol from Mylia taylorii (Liverwort) Containing Two Conjugated Cyclopropane Rings. Revision of a Proposed Structure. Chem. Commun. 1976, 1006. 

I-)-Cubetol (535) was a tricyclic monohydric alcohol from a Ce-spitularia species 394). A sample of Clavularia inflata yielded two sesquiterpenes closely related to sinularene, 12-acetoxycyclosinularane (536) and 12-acetoxysinularene (537) (422). Compound 537 could be derived from 536 by opening of the cyclopropane ring. Another species of the order Stolonifera, C. koellikeri yielded the methyl ester (538) 422). 

Fig. 3.8 Cyclopropanation of styrene in the presence of alcohol ligands. [Yang, Z. Lorenz, ).C. Shi, Y. Tetrahedron Lett. 1998, 39, 8621. Reprinted with permission from Elsevier Ltd.)...

The next step in the calculations involves consideration of the allylic alcohol-carbe-noid complexes (Fig. 3.28). The simple alkoxide is represented by RT3. Coordination of this zinc alkoxide with any number of other molecules can be envisioned. The complexation of ZnCl2 to the oxygen of the alkoxide yields RT4. Due to the Lewis acidic nature of the zinc atom, dimerization of the zinc alkoxide cannot be ruled out. Hence, a simplified dimeric structure is represented in RTS. The remaining structures, RT6 and RT7 (Fig. 3.29), represent alternative zinc chloride complexes of RT3 differing from RT4. Analysis of the energetics of the cyclopropanation from each of these encounter complexes should yield information regarding the structure of the methylene transfer transition state. 

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