L- cyclobutanol

In some cases the Grignard reaction can be performed intramolecularly.396 For example, treatment of 5-bromo-2-pentanone with magnesium and a small amount of mercuric chloride in THF produced 1-methyl-l-cyclobutanol in 60% yield.397 Other four- and five-membered... 

Write out a synthesis of 2,5-diphenylfuran from 1,2-diphenyl-l-cyclobutanol. 

A combination of a Pd-catalyzed nucleophilic substitution by a phenol and a ring expansion was described by Ihara and coworkers [127] using cis- or trans-substituted propynylcyclobutanols 6/l-262a or 6/l-262b. The product ratio depends on the stereochemistry of the cyclobutanols and the acidity of the phenol 6/1-263. Thus, reaction of 6/l-262b with p-methoxyphenol 6/1-263 (X = pOMe) led exclu-... 

Scheme 9.—Proposed Mechanism for Formation of Cyclobutanol from the Photolysis of 1,3,4,5,6-Penta-O-acetyl-fceto-L-sorbose (18).

Another example of a diene undergoing a [2 + 2] cycloaddition reaction with an alkene has been reported recently4. 2-Dimethylaluminumoxy-l,3-cyclohexadiene (7) reacted with phenyl vinyl sulfoxide (8) to afford a diastereomeric mixture of cis substituted cyclobutanols 9 (equation 3). The occurrence of a [2 + 2] cycloaddition as well as the high cis stereoselectivity observed were explained by a pre-organization of the reactants by complexation of the diene bound aluminum with the sulfoxide oxygen on the olefin. 

Figure 1 shows the X-ray crystal structure of the (R)-(+)-l-phenylethyl-amine salt of keto-acid 37a prior to reaction and following 70% conversion to the corresponding cyclobutanol 38b. The structure of the mixed crystal is... 

Cyclobutanol formation is not usually an efficient process for simple aliphatic ketones. It has, however, been shown12 that irradiation of the urea inclusion complex of 5-nonanone is more effective, providing l-butyl-2-methylcyclobutanol in 40% yield, with the balance of the ketone undergoing photochemical fragmentation. The cyclobutanol product is a 97 3 cisjtrans mixture. In the absence of urea, photolysis proceeds to give the cyclobutanol in 24% yield, as a 60 40 cisjtrans mixture. Photocyclization has also been improved by inclusion in zeolites13. 

Diketones cyclize much more efficiently than simple ketones. Photochemical cyclobutanol formation is the key step in a novel route14 to 1,3-cyclopentanediones, as exemplified by the conversion of l-bromo-5-phenyl-2,3-pentanedione to 4-phenyl-l,3-cyclopentanedione. 

Another convenient method for the preparation of functionalized cyclobutanol derivatives is by treatment of 1,2-diphenylethylene acetals containing a 1,3-dithiane moiety in the y-position, e.g. 14c. with butyllithium. The isolation of 2,2-(propane-l,3-diyldisulfanyl)cyclobutanol (15c) together with benzyl phenyl ketone in 90 and 92 % yield, respectively, indicates that the reaction mechanism should involve the intramolecular attack of the metalated dithiane on the acetal carbon atom with concomitant hydride shift at the acetal group.15... 

Cyclooctadecane-l,10-dione (8) undergoes isomerization to cyclobutanols on irradiation. In... 

Dihydro-2,3-methano-l,4-naphthoquinones 15 rearrange to cyclobutanols 16 on irradiation. The reaction is. at least in part, reversible, as the excited cyclobutanol undergoes ring opening and disproportionation back to starting material.15 16... 

Byproducts of this rearrangement are cyclobutenes, cyclopropane derivatives and allenic alcohols. The ratio of these products depends on the substitution of the substrate and on the reaction conditions. For example, 3-methyl-5-tosyloxypenta-l,2-diene (3) gives 75% of 1-methyl-2-methylenecyclobutanol (4) upon hydrolysis with water and calcium carbonate at 100 °C, while acetolysis with acetic acid/sodium acetate at 80 °C, and subsequent treatment with lithium aluminum hydride, provides only 37% of the cyclobutanol.12... 

Solvolysis of l-ethenylidene-3-tosyloxycycloalkanes 13 gives cyclobutanols of the bicy-clo[n.l.l]alkanol and bicyclo[n.2.0]alkanol series.14 In this reaction, the competing 1234-1243 rearrangement leads to the bicyclo[n.2.0]alkanols 15. The yield for the homoallyl rearrangement product 14, after hydrolysis, is 9% when n = 3 and 37% when n = 4. 

Similarly, deamination of cyclobutylamine with nitrous acid resulted in the formation of but-3-en-l-ol in 4% yield.5 Reaction of cyclobutanol with thionyl chloride led to equally small amounts of l-chlorobut-3-ene, regardless of the reaction conditions.6... 

A similar example is the ring expansion of cyclobutanone via l-tris(methylsulfanyl)methyl-cyclobutanol (6) to 2,2-bis(methylsulfanyl)cyclopentanone (7).43 The use of Af,A-diisopropyl-ethylamine is unneccessary in this reaction as the hydroxy group has already been deprotonated with butyllithium. Further examples of this type of reaction can be found in refs 43 and 44. 

Am cyclohutanol. A 1-L, three-necked, round-bottomed flask equipped with a reflux condenser and a magnetic stirring bar is charged with 600 mL of water, 57.5 mL (ca. 0.68 mol) of concentrated hydrochloric acid, and 57.7 g (0.80 mol) of cyclopropylcarbinol (Note 1). The reaction mixture is stirred and refluxed for 3 hr. Cyclobutanol is only partially soluble in water and soon separates. The reaction mixture is allowed to cool to room temperature and the flask is then immersed in an ice bath. To the cold, stirred mixture is added 24 g (0.6 mol) of sodium hydroxide pellets, followed by 6.7 g (0.08 mol) of sodium bicarbonate to complete the neutralization. The mixture is saturated with sodium chloride and extracted for 30 hr with diethyl ether using a liquid-liquid continuous extraction apparatus. The ethereal extract... 

A 25-m x 0.3-mm HP Ultra Silicone capillary column at 70°C with 30 psi helium head pressure was used for the chromatographic analysis retention times of 3-buten-l-ol and cyclobutanol are 1.19 min and 1.35 min, respectively. The submitters used a 3-m x 0.3-cm 20 M carbowax column at 90°C/8 psi hydrogen and they reported retention times of 13 m1n and 20 min for 3-buten-l-ol and cyclohutanol, respectively. 

The crude product was first distilled on a 50-cm x 0.8-cm spinning band column (reflux ratio 10 1) to give 19.6 g of cyclohutanol, bp 124°C. The forerun fractions, bp 66-123°C (23.0 g), were combined and redistilled on a 30-cm x 0.8-cm spinning band column (reflux ratio 25 1) to give an additional 13.2 g of cyclobutanol, bp 122-123°C. The major by-product, 3-buten-l-ol,... 

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