Dihaloalkane derivatives

In view of the ready availabiUty of optically pure lactic acid derivatives this reaction offers an attractive general method for the preparation of optically pure aromatic ester derivatives (41). Stereoselective alkylation (15—60% inversion) of ben2ene with optically active 1,2- 1,3- and 1,5-dihaloalkanes was also reported (42). 

Each of the following dihaloalkanes gives an A-(haloalkyl)phthalimide on reaction with one equivalent of the potassium salt of phthalimide. Write the structure of the phthalimide derivative formed in each case and explain the basis for your answer. 

Thermolysis of the dicarbamic acid silyl ester (CH2 N[SiMe3]C02SiMe3)2) gives the 1,3-diazetane derivative 26 <96JOM93>. Alkylation of the 1,3-dithietane tetraoxide 27 with a,co-dihaloalkanes yields the dispiro compounds 28 (n = 1-4) <95ZOR589>. The first 1,2-dithiete S-oxide 29 is reported <95TL8583>. 

Whereas alkylation of activated methylene systems by classical methods produces a mixture of mono- and dialkylated products, with the latter frequently predominating, phase-transfer catalytic procedures permit better control and it is possible to obtain only the monoalkylated derivatives. Extended reaction times or more vigorous conditions with an excess of the alkylating agent lead to dialkylated products or, with dihaloalkanes, carbocyclic compounds as the technique mimics dilute concentration conditions, e.g. the resonance stabilized cyclopentadienyl anion, generated under solidiliquid two-phase conditions, or under liquiddiquid conditions, reacts with 1,2-dihaloethanes to form spiro[2,4]hepta-4,6-diene (70-85%) [1-3]. Reaction with dichloromethane produces bis(cyclopenta-2,4-dien-l-yl)methane (60%) [4],... 

Methylene groups can be dialkylated if sufficient base and alkylating agent are used. Dialkylation can be an undesirable side reaction if the monoalkyl derivative is the desired product. Use of dihaloalkanes as the alkylating reagent leads to ring formation, as illustrated by the diethyl cyclobutanedicarboxylate synthesis (entry 7) shown in Scheme... 

First, when 1,1-dihaloalkanes are reduced with low-valent titanium derived from TiCU and zinc, it is necessary to add a catalytic amount of PbCU (or Pb) for reproducibility (Equations (5) and (6)). Two kinds of zinc powder are available for laboratory use electrolytic zinc derived by hydrometallurgy and distilled zinc derived by pyrometallurgy. 

Reaction of 91 with methacrylic acid gives rise to double unsaturated side-chain compounds (93) these were subjected to polymerization.185 Subjecting isosorbide to etherification with a, m-dihaloalkanes, mono- and dialkyl derivatives were obtained. These could not be transformed into polyethers. The use of tram-1,4-dichlorobutene lead to oligomers up to the... 

Significantly, derivative 22 can be used as a precursor to other macrocycles featuring the l,l -diphosphole moiety. For example, the reductive cleavage of the two P-P bonds with sodium gave the dianion 24, which, upon reaction with 22, afforded the dianion 25 (Scheme 4.8) [28c]. Derivative 25 is a versatile nucleophile that reacts with tetrachloroethylene and dihaloalkanes to give the novel macro-... 

Perkin ring synthesis using DiTOX. Anions derived from DiTOX undergo efficient Perkin ring synthesis on treatment with dihaloalkanes to provide cycloalkane rings of up to seven members (Table 12).59... 

When the electrophile is a dihaloalkane R-CHXY, the ensuing exo-halomethyl derivative (39) undergoes a metal-assisted solvolytic ring-expansion reaction in polar solvents to... 

Table 1 lists the experimental conditions for the electrochemical formation of a cyclopropyl ring from a variety of 1,3-dihaloalkanes, mostly from dibromoalkyl derivatives. A free cyclopropyl ring as well as a spiro derivative (entry 6), bicyclobutanes (entries 8-10) and other fused and highly strained systems such as tricyclene (entry 11) and a propellane derivative (entries 12,13) were obtained. In addition, Carroll and Peters have found evidence for the intermediacy of [2.2.1 ]propellane upon reducing 1,4-dihalonorbor-nanes electrochemically at a low temperature, although attempts to isolate it were unsuccessful. The intramolecular electrochemical reduction of a dihalo-substituted tricyclic compound leads to cyclization with formation of a tetracyclic derivative in which... 

The reaction of r/cm-dihaloalkanes with alkyl or aryl aldehydes and ketones under Barbier conditions with Mg/Hg can be used to prepare unsaturated derivatives in a Wittig-type reaction. Some Japanese researchers [71] show that styrene and substituted styrenes, as well as octenes, can be prepared in yields as high as 75% using diiodomethane and the corresponding aldehydes [Eqs. (32) and (33)]. 

In most cases, bromo or chloro derivatives are used as starting materials. The 1,2-dihaloalkanes are usually prepared from the alkenes by halogen addition, the 1,1-dihaloalkanes from the corresponding carbonyl compounds with PCI5 or other acid chlorides (Scheme 31). Some 1,1-dichloroalkanes can be prepared from vinyl chloride by addition of a secondary or tertiary alkyl chloride (Scheme 32). The 1-haloalkenes can be prepared from either the 1,2- or the 1,1-dihaloalkanes by elimination of 1 mol of hydrogen halide or by a Wittig reaction (Scheme 33). 

Friedel-Crafts alkylations with higher dihaloalkanes generally give a mixture of products derived from processes such as isomerization, multiple addition and dehydrogenation (caused by AICI3), as seen from the examples shown in equations (73) and (74). ... 

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