L- cyclobutene

Asymmetric deprotonation of monocyclic cycloalkanones is not restricted to cyclohexanones. Thus, deprotonation of 3-phenylcyclobutanone with lithium bis[(S)-l-phenylethyl]amide in THF at — 100 °C in the presence of chlorotriethylsilane affords (—)-(/ )-3-pheny 1-1 -(triethylsi-lyloxy)-l-cyclobutene with 92% ee in 70% yield59d. Interestingly, with lithium (/ )-2,2-dimethyl-A-[( / )-2-(4-methyl-l-piperazinyl)-l-phenylethyl]propylamidc in THF/HMPA an ee value of only 47 % for the enol ether is recorded. 

Cyclobutene-1,2-dicarboxylic acid l-Cyclobutene-l,2-dicarbox-ylic acid (8,9) (16508-05-7)... 

Sulfuric acid converts 3,3-difluoro-2-ethoxy-l-phenyl-l-cyclobutene to a fluorine-free product. What is the compound N and how is it formed ... 

Bis(trimethylsiloxy)cyclobutene Silane, (l-cyclobuten-l,2-yle-nedioxy)bis[trimethyl] (8) ... 

Another example of the preceding valence isomerization via phos-pha Cope rearrangement, shown in Scheme 7, is the transformation of 3,4-diphospha-l,5-hexadiine to the hexatetraene followed by a [2 + 2] cycloaddition to give 3,4-bis(phosphamethylene)-l-cyclobutene (109). 

The epoxidation reactions of a series of m-3,4-disubstituted-(CH2X)-cyclobutenes 6-11 with DMDO and MCPBA have been investigated by Freccero et a/. <1999X11309>. A remarkable ry -diastereoselectivity in the formation of the epoxide has been observed for substrates bearing electron-withdrawing substituents. Transition structures for epoxidations of 3,4-dimethylcyclobutene 6 and 3,4-bis(mesyloxymethyl)-l-cyclobutene 11 with dioxirane and peroxy-formic acid have been located with the B3LYP/6-31G method (Table 1). 

Hayashi, K.-L, Shinada, T., Sakaguchi, K., Horikawa, M., and Ohfune, Y., Olefination of dialkyl squarates by Wittig and Homer-Emmons reactions. A facile synthesis of 3,4-dioxo-l-cyclobutene-l-acetic acid esters. Tetrahedron Lett., 38, 7091, 1997. 

Dioxo-compounds ox. cleavage, 137 synthesis via l-cyclobutene-l,2-diol derivs.,... 

Silane, [l-cyclobutene-1.2-diylbis(oxy)]bis[trimethyl] [17082-61-0], 60, 19 Silane, (l-cyclopenten-l-yloxy)trimethyl- [19980-43-9], 62, 100 Silane, (l-cyclohexen-l-yloxy)trimethyl- [6651-36-1], 60, 118 Silane, [(1-ethoxycyclopropyl)oxy]trimethyl- [27374-25-0], 63, 153 SILANE, [(1-ETHYL-1-PROPENYL)OXY]TRIMETHYL-. (Z)- [51425-54-8], 61, 122 SILANE, [(3-METH0XY-1-METHYLENE-2-PR0PENYL)0XY]TRIMETHYL-[59414-23-1], 61, 147... 

Draw (a) 1-acetyl-l-cyclobutene, (b) 2,4-dimethylcycIohept-4-enone, and (c) cyclopent-3-en-l-carboxaldehyde. 

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