Dichlorocyclopropanation of Simple Olefins

The dichlorocyclopropanation of simple olefins is characterized by good yields, convenient reaction conditions and inexpensive reagents. When there is more than one isolated double bond in a substrate, products of both mono and multiple cyclopropanation are isolated unless a selective catalyst is used (see above). Examples of the simple dichlorocyclopropanation reaction are presented in Table 2.1. Examples of multiple dichlorocyclopropanation are recorded in Table 2.2. Imines also add dichlorocarbene and are discussed in Sect. 3.4. 

Number Olefin of carbons % Yield Catalyst Refer- ences 

There are several phase transfer cyclopropanation reactions which deserve special comment. For example, addition of dichlorocarbene to the conjugated carbon-carbon double bond of styrene systems goes in excellent yield. Addition of dichlorocarbene to 1,2-dihydronaphthalenes [24] and to indenes [23] led to the expected 1,1-dichlorocyclopropane adducts. Heating the 1,1-dichlorocarbene adducts of indenes with ethanolic KOH provides an efficient route to 2-chloronaphthalene derivatives [23] (see Eq. 2.14). 

Addition of dichlorocarbene to phenyl substituted methylene cyclopropanes provides an efficient route to l,l-dichloro-2-phenyl-spiropentanes [26] (see Eq. 2.15). 

Three examples of selective mono adducts of dichlorocarbene to carbon-carbon double bonds in the side chain of steroidal systems have been reported [4]. In each case, the arrow indicates the site of addition. 

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Dichlorocyclopropanation of Simple Olefins Table 2.1. Dichlorocyclopropanation of simple olefins... 

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