1- Bromo-3-chlorocyclobutane, with

Bromo-3-chlorocyclobutane, with sodium to give bicyclo [1.1.0]-butane, 51, 55... 

Wurtz reaction The coupling of two alkyl halides, RX, with sodium metal to give the R-R compound. Usually of almost no synthetic value as there are many side reactions. However, the intramolecular reaction of l-bromo-3-chlorocyclobutane with sodium gives bicyclobutane in about 95% yield. 

Deoxyiodination has been used for the synthesis of 17 (n = 4). ° For the preparation of bi-cyclo[1.1.0]butane 17 (n = 1) and congeners thereof, special conditions are required. Reaction of l-bromo-3-chlorocyclobutane with sodium in refluxing dioxane gave bicyclo[l. 1. OJbutane in 90% yield a detailed experimental procedure is given.Hexamethylbicyclo[l, 1.0]butane was similarly obtained in 75% yield using sodium-potassium alloy in 1,2-dimethoxyethane. ... 

Boron trifluoride etherate, co-catalyst, 53, 30, 32 a-Bromination, selective of aralkyl ketone, 53, 111 Bromine, with 3-chlorocyclo-butanecarboxylic acid and mercuric oxide to give 1-bromo-3-chlorocyclobutane, 51, 106... 

Chlorocyclobutanecarboxylie acid, with mercuric oxide -and bromine to give 1-bromo-3-chlorocyclobutane, 51, 106... 

With l-bromo-2-chlorocyclobutane there are cis and trans isomers and both substituted C s are chiral. Both geometric isomers form racemic mixtures. 

Draw the products from the reaction of frarcs-2-bromo-4-chlorocyclobutan-one with LiAlH4 by attack from the Re and from the Si sides. Deduce the absolute configuration of the reaction products. 

HunsdieckerCristol reaction. (1, 657). A detailed procedure for the preparation of l-bromo-3-chlorocyclobutane by the modified Hunsdiecker reaction has been published.1 A 1-1. three-necked, round-bottomed flask wrapped with aluminum foil to exclude light and equipped with a mechanical stirrer, a reflux condenser, and an addition funnel, is charged with 37 g. (0.17 mole) of red mercuric oxide and 330 ml. 

It is instructive to compare the stereoisomers of 2-bromo-3-chlorobutane with those of a cychc analog, l-bromo-2-chlorocyclobutane (Figure 5-9). In both cases, there are four stereoisomers RJt, S,S, R,S, and 5,/f. In the cyclic compound, however, the stereoisomeric relation of the first pair to the second is easily recognized One pair has cis stereochemistry, the other trans. Cis and trans isomers (Section 4-1) in cycloalkanes are in fact diastereomers. 

---