[80411-43-4]  · C3H4ClLi  · 1-Chloroallyllithium  · (MW 82.46)

(reacts with substituted epoxides,4 thiiranes,5 esters,1 alkyl bromides,6 imines,10 and azirines10 in the a-mode; with carbonyl compounds2 and alkyl halides3 gives a mixture of a- and g-adducts; 1-chloroallylzinc gives highly diastereoselective a-addition with aldehydes and ketones7)

Solubility: sol diethyl ether, THF.

Handling, Storage, and Precautions: highly unstable; generated at -78 °C in the presence of electrophiles in an inert atmosphere.

Chloroallyllithium was first prepared1 by treating g-chloroallyltriphenyllead (1) with n-Butyllithium at -90 °C (eq 1). Reaction with various electrophiles gives products arising from both a- and g-attack.1-4 However, (2) displays exclusive a-selectivity in its reaction with epoxides to give either the corresponding b-chloro-g-ethylenic alcohols (3) or a mixture of (3) and the cyclized products (oxetanes) (4) (eq 2).

Similarly, the reaction with thiiranes gave 2-vinylthietanes (7) by intramolecular cyclization of the initially formed b-chloro-g-ethylenic thiolithium (6) (eq 3).5 The a-regioselectivity was also observed in the acylation of (2) with esters (except with t-butyl carboxylate). a-Chloro-a,b-unsaturated ketones (9)1 were formed by base-catalyzed isomerization of initially formed a-chloroacyl adducts (8) (eq 4).

Alkylation of a-chloroallylithium gave mixtures of a- and g-alkylated products (10) and (11) (eq 5).3 However, with a few alkylating agents, a high degree of a- (n-butoxymethylene chloride) or g- (dimethylmethyleneammonium iodide) regioselectivity was observed. The g-alkylated products are formed exclusively in the (Z) configuration, which is explained on the basis of transition state (12) (eq 5).

Subsequently, 1-chloroallyllithium was directly generated in situ by treating Allyl Chloride with Lithium Diisopropylamide at -78 °C and was shown to undergo alkylation with high a-regioselectivity with a variety of primary alkyl bromides.6 The secondary allyl chloride intermediates (13a) and (13b) have been used as building blocks for the synthesis of disubstituted alkenic insect sex pheromones of A. leucotreta (14a) and S. littoralis (14b), respectively (eq 6). The a-alkylation/cuprate displacement sequence is also applicable to anions of methallyl and crotyl chloride and is a promising route for the synthesis of more complex systems (eq 7).6

The chloroallyllithium (2) derived from (1) and butyllithium adds to carbonyl compounds to form products of both a- and g-addition in varying proportions (eq 8).2 The epoxides (19) thus obtained were a mixture of (E) and (Z) isomers, while the cis configuration was maintained in the g-adducts (20), as observed earlier (eq 8).

Interestingly, the anion (21) with a Zn2+ counterion reacts with aldehydes and ketones with exclusive a-addition and with high diastereoselectivity in the product chlorohydrins (eq 9).7 No epoxides were formed with Zn2+ as counter cation. Treatment of the chlorohydrins (22) with potassium ethoxide gave cis-vinyloxiranes (19) in quantitative yields (eq 9). Chloroallyllithium (2) generated by direct deprotonation of allyl chloride with LDA, however, gave only g-adducts (20) with aromatic aldehydes and ketones (eq 10),7 in contrast to the ambident behavior of (2) generated from (1).2

The anion (2) underwent regioselective a-addition with imines8,9 and azirines,10 followed by intramolecular cyclization to afford the corresponding vinylaziridines (24) (eq 11) and 2-vinylazabicyclobutanes (26), respectively (eq 12).

Related Reagents.

Allyllithium; Dibutyl Telluride; 1,1-Dichloroallyllithium.

1. Mauze, B.; Doucoure, A.; Miginiac, L. JOM 1981, 215, 1.
2. Doucoure, A.; Mauze, B.; Miginiac, L. JOM 1982, 236, 139.
3. Mauze, B.; Ongoka, P.; Miginiac, L. JOM 1984, 264, 1.
4. Ongoka, P.; Mauze, B.; Miginiac, L. JOM 1985, 284, 139.
5. Ongoka, P.; Mauze, B.; Miginiac, L. S 1985, 1069.
6. Macdonald, T. L.; Amirthalingam Narayanan, B.; O'Dell, D. E. JOC 1981, 46, 1504.
7. Mallaiah, K.; Satyanarayana, J.; Ila, H.; Junjappa, H. TL 1993, 34, 3145.
8. Mauze, B. JOM 1980, 202, 233.
9. Doucoure, A. Dissertation, Université de Poitiers, 1982.
10. Mauze, B. TL 1984, 25, 843.

H. Junjappa, H. Ila, & J. Satyanarayana

North-Eastern Hill University, Shillong, India

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