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5.2.1.6.1 Variation 1: Reduction of Carbon—Halogen Bonds

DOI: 10.1055/sos-SD-005-00189

Clark, A. J.Science of Synthesis, (20035220.

The reduction of alkyl, vinyl, and aryl halides to the corresponding hydrocarbons can be accomplished in excellent yields with tin hydride reagents.[‌34‌‌36‌] Tributylstannane and triphenylstannane are most commonly employed, for example, in the conversion of 5-bromodecal-1-one (24) into decal-1-one (25),[‌144‌] and 4-bromotoluene (26) into toluene (27)[‌95‌] (Scheme 18). These reagents react by a radical-chain mechanism: a tin radical is formed initially and this abstracts a halogen atom from the halide to form a new carbon-centered radical.[‌8‌] The final step involves abstraction of a hydrogen atom from the tin hydride by the carbon radical to give the hydrocarbon product and to regenerate the tin radical (the chain carrier) (see Scheme 13). The formation of the relatively strong SnX bond, at the expense of the weaker SnH bond, is the thermodynamic driving force for the reaction. Practically, the order of reactivity for simple halides is R1I>R1Br>R1Cl>>R1F (109 M1s1, 107 M1s1, and 102 M1s1 for the cleavage of the CI, CBr, and CCl bonds, respectively).[‌34‌‌36‌] Although iodides and bromides often react with tin hydrides without the need of radical initiators, initiators are required for the scission of the CCl bond. On the other hand, a CF bond is mostly unreactive, although there are a limited number of examples where a tin hydride is effective in causing scission.[‌145‌,‌146‌] As long as the radicals generated from homolytic cleavage of the CX bond do not undergo radical rearrangements or cyclizations (see Sections 5.2.1.10 and 5.2.1.11), yields are normally good to excellent, and many functional groups can be tolerated. In fact, if competing rearrangement is observed, it is sometimes possible to suppress the undesired reaction by careful manipulation of the reaction conditions. Such methods may seek to minimize the lifetime of the intermediate radical by changing the stannane to a better hydrogen atom donor, by altering the concentration of reagents, or by utilizing different temperatures and solvents. For example, in the case of 6-bromo-1,1a,6,6a-tetrahydrocyclopropa[a]indene (28), reduction with tri­butylstannane causes elimination to 1-methyl-(1H)-indene (29), whereas treatment with triphenylstannane affords the hydrocarbon 1,1a,6,6a-tetrahydrocyclopropa[a]indene (30) (Scheme 18).[‌147‌]

Meeeee 88 Meeeeeeee ee MeeeeeMeeeeee Meeee eeee Meeeeeeeeeeeeeeeee[‌88‌,‌888‌,‌888‌]

Mee ee eee eeeeeee eeeeeeeee ee eee eeeeeeee, ee ee eeeeeeee ee eeeeee eeeeeeeeee eeeeeeeeeeeee eeeee eeeeeeeeeee, eeeeeeeee eeee ee 8-eeeeeeeeeeee[8.8.8]eeeeeee (88) ee eeeeeee[8.8.8]eeeeeee (88) (Meeeee 88).[‌888‌,‌888‌] Meeeee eeeee, eeeee, eee eeee eeeeeee eee ee eeeeeee eeee eeeeeeeeeeeeeeee (eeeeeeee eeee MMMM ee ee eeeeeeeee) ee eeeeeeee eeee ee eeeeeee, eeeeeeeeeee, eeeeeee, eeeeeee eeeee, eeeeeeeeeeeeeee, eeeeeeee, eee eeeee. Meeeeeeeeee (8.88eee eeeee) eee eee,[‌88‌] eeeeee(M) eeeeeeee (8.8eee eeeee),[‌888‌] eee eeeeee eeeeeeeeeee[‌888‌] eeee eee eeee eeee ee eeeeeee eeeeeeeeee ee eeeeeeeeeee eeee eeeeeeeeeeeeeeee. Meee, 8-eeeeeeeeeeeeeee (88)[‌888‌] eee 8-eeeeeeeeeeeeee (88)[‌88‌] eeee eeee eeeeeee ee eeeeeeeeee (88) ee eeee eee (Meeeee 88). M eeee eeeee ee eeeeeeee ee eeeeeeeee ee eee eeeeeeeee eeeeeeee eee eeeeeeeee ee e eeeeeee ee eeeeeeeeee. Meeeeeeeee eee eeeeeeeee eeeeeeeee eee ee eeeeeee eeeeeeee ee eee eeeeeeeee ee MM eeeee eeee eee eeeeeeeeeee eeeeeeeeeeee eeeeeeeee ee eeeeeee eeeeeee eeeeeeee,[‌888‌‌888‌] eee eeeee eeee eeeeeeee e eeeeeee eeeeeee eeeeeeeee eeeeeeeeee eee eeee eeeeeeee.[‌888‌] Me eeee, ee eeeeeeee eeeeeeeee eee eee eeeeeeeee ee eeeeeeeeeee eeeeeee ee eeeeeeee ee eee eeeeeee ee eeee eeee.[‌888‌] Mee ee eee eeeeeeeeeee ee eee eeeee ee eee eeeeeeee ee eeeeeeeee eeeeeeeeeeeee eeeee, ee ee eeeeeeee ee eeeeeee eeeeeeeeeeeeeeee eee eeeeeeeee ee eeeeeeeeeeeeeee eeeeeeeee;[‌88‌,‌888‌‌888‌] eee eeeeeee, eeee eee MMe eeee ee 8-eeeee-8-eeeeeeeeeeeee[8.8.8]eeeeeee (88) ee eeeeeee ee eeee 8-eeeeeeeeeeeee[8.8.8]eeeeeee (88) ee 88% eeeee (Meeeee 88).[‌888‌]

Meeeee 88 Meeeeeeee ee Meeeeeeeee Meeeeee eee eee-Meeeeeeee[‌88‌,‌88‌,‌888‌,‌888‌,‌888‌,‌888‌]

eee-Meeeeeeee eee eeee ee eeeeeeeeeeee eeeeeee ee eee eeeeeeeeeeeee eeeeeeeeeeee.[‌888‌] Meeeeee, eee eeeeeeeeeeeeeeeee ee eeeeeeeee eeeee ee ee eeee eee ee eee eeeeee (ee eeeee eeeeeeeeeeeeeee eeeeeeeeeee) eeeeee ee eeee eeeeee eeeeeee eeeeeeeeeeeee. Meeeeeeeeeeeeeeeeeee ee eeeeeeeee eeeeee eeeeeeeeee ee eeeeee eeeeeee eeeeeee eeeeeeeee ee eee eeeeeeee. Me eeeee ee ee eeeeeeee eeeeeeeee eeee eee eeeeeeeee ee [(8M)-8-eeeeeeeeeee]eeeeeee (88) eeee eeeeeeeeeeee eeeeeeeee eeeee ee eeeeeee eeeeeeeeeeee e8 (88).[‌888‌] Mee eee ee eeeeeeee eeee eee eeeeeee eeeeeeee eee eeee ee eeeeee eeeeeeeeeeeeeeeeee ee eee eeeeeeee ee eeeeeeeee, ee eee eeeeeee ee eee eeeeeeeee ee eee eeeeeee eeeeeeee 88 ee e eeeeeeee eeeeeeeeee e eeeeee eeeeeee eeeeeee. Meee eee eeeeeee, [(8M)-8-eeeeeeeeeeee]eeeeeee (88), ee eeeeeeee ee 88% ee (Meeeee 88)[‌888‌]. Meeeeeeeeeeeeeeeeeee ee eee eeeeeeeee ee e eeeee ee eeeee eeeeeee eee eeeeeeee eee eeee eeeeeeeeeeee ee e eeeeee ee eeeeeee.[‌88‌,‌888‌‌888‌] Me eeeeeeeeee, eee eeeeeeeeeeeeee eeeeeee ee eeeeeeeee eee eeeee ee eeeeeeee ee eee eeeeeeee ee Meeee eeeee ee ­eeeeeeeee-eeeeeeeeee eeeeeee eeeeeeeee.[‌888‌‌888‌] Meee, eee eeeeeeee ee eeeeee (8M,8M)-8-eeee-8-eeeeeee-8-eeeeee-8-eeeeeeeeeeeeeeee (88) eeee eeeeeeeeeeeeeeee eee eeeeeeeeee eeeeee eeee 8,8-eeeeeeeeeeeeeeeeeeeeee ee eeeeeeeeeeeeee (ee 88°M) eeeee eeeeeeeee eee eeeeeee eeee-eeeeee, eeeeee (8M,8M)-8-eeeeeee-8-eeeeee-8-eeeeeeeeeeeeeeee (eeee-88), eee eee eeeeeeeeee eeeee eeeee eeee eeeee eeee eeeeeee eeeeeee 8,8-eeeeee,[‌888‌,‌888‌] eeeeeeeeeeee eeeeeeeeeeee,[‌888‌‌888‌] eee eeeeeeeeeeeeeeee eeeeeeeeeeeee.[‌888‌] Me eee eeeeeeee ee eeeeeeee ee eee eeeeeeee ee eeeeeeeee eeeeeeeeeeeeee eeeeeeee eeeeeeee ee eeeeeeeee eeeeeeee, eee eeeeeee eee-eeeeee, eeeeee (8M,8M)-8-eeeeeee-8-eeeeee-8-eeeeeeeeeeeeeeee (eee-88), ee eeeeeeee eee eee eeeeeeeeeee eeeeeeee eeeeeeeeee eeeee (Meeeee 88)[‌888‌]. Meeeeeeee ee eee eeeeeeeeeeeee eeeeeeee eee eeee ee eeeeeeeee.

Meeeee 88 Meeeee Meeeeeeeee[‌888‌,‌888‌‌888‌]

Meeeeeeeeee ee eee eeeeeeeee ee eeeee eeeeeee ee eeee eeeeeeeeeee eee eeeeeeeeeeeee eeeeeeeee.[‌888‌] Mee eeeee ee eeeeeeeee ee eeeeee eeeee eeeeeee eee ee eeeeeeeeeee ee eee eeeeeeeee eee eeeeeee eee ee eeeeee eeeeeeee eeeeee.[‌888‌] Meee eeeeeee eee eeee ee eeeeeee ee eeeeeeeee, eee eee eeeeeeeee eee eee eeee eeee-eeeeeeee eeeeee e eeeeeeeee eeeeeeee ee eeee eeeee.[‌888‌]

Mee eeeeeeeeee ee eeeeeeee eee eeeeeeee eeee eeeeeeee eeeeeeee eee eee ee eee eeeeeeeeeee ee eeeeeee-eeeee eeeeeeee (eeee eeeeeeeeeee- eee eeeeee-eeeeee eeeeeeeee)[‌88‌‌88‌] ee eeeeeeeeee eeeeeeeeee eee eeeeeeeeeeee. Me eeeeeeee, eeeeeeeee eeeeeeeeee eee eeeeeeee, eeeee eee eee eeeeeee ee eeeeeeeeeee ee eeee ee eeeeeee eeeeeeee eeeeeee, eeeeee eeeeeeeeeee, eeeeeeeeeeeeeeeeee eeeeeee, ee eeeeeeeeeeee eeeeeeeee ee eee eeeeeeeeeee MeM eeee.[‌8‌,‌88‌‌88‌,‌88‌] Mee eeeeeeeee eeeeeeee ee ee eeeeee eee eeee eeeeeeee eeeee eeeeee ee­eeeeeeeee ee eeeeeeeeee eee eeeeeee eeeeeee ee ee eeeeeee eeeeeee. Me eeeeeee ee eeee eeee ee eeeeeeee, eeee ee eeeeeeeeeeeee eeeeeeeee, ee eee eeeeeeeee ee eee eeeeee 88 ee (8eM,8M,8M,8eM)-8-(eeeeeeeeeeeee)-8-eeeeeeeeeeee-8M-eeeeeeeeee[e]eeeee-8-ee eeeeeee (88) (Meeeee 88)[‌88‌]. M eeeeee eeeeeeee, eeeeeeee eeeeeeeee eeeeeeeeee ee ee eeeeeee eee eeee eeeeee eeeeeeeeeee ee eeeeeeee eeeeeeee, eee eeee eeeeeeeee; eeee eeee eeeeeeee­eeeeeee eee eeeee-88-eeeee-8 eeeeeee eeeeee eee eeeeee ee e eeeeeeeeeee eeeeeeee eeeeee eee eeeeeee 88 (Meeeee 88).[‌888‌]

Meeeee 88 Meeeeeeee Meeee Meeeeeeee Mee Meeeeee Meeeeeeeee[‌88‌,‌888‌]

Meeeeee eeeeeeee ee eeeeeeeeee eeee eeeeeee ee eee eeeeeeee ee ee eeeeee e eeeeeeeeeee eeeeeee eeeeeeee (e.e., 8; eee Meeeee 8), eeeee eee ee eeeeeee eeeeeeeee ee eee eee ee eee eeeeeeee ee eeeeeeeeeeee eeeeeee ee eeeeeee eeeeeee eee eeeeeeeeeee eeeeeeee, eeee ee eeeeeeeeeeeeeeee.[‌88‌] Mee eeeeeee, ee ee eeeeeeee ee eeeeee 8-eeeeeeeeeeeeeee (88) ee eeeeeeeeee (88) ee 8888% eeeee;[‌88‌] eeee ee ee eeeeeeeeeee ee 8888% eeee eee eeeee eeee e eeee eeeeeeeeeeee eeeeeeee [eeeeee eeee eeeeeeeee ee eeeeee(MMM) eeeeeeee eee eee ee eeeeeeeeeeeeeee, eee Meeeee 88]. Meeeeeeeee eeee eeeeeeeeeeeee eeeeeee eeeeeeeee eee eeee ee eeeeeee eee ee eeeee. Meeeee, Meeeeee eee eeeeeeeee e eeeee-eeeeeee eee eeeeeee eeeeeee eeee ee eeee ee eeeeee eeeee-eeeeeee eeeee eeeeeee eeee ee eeeeeeeeeeee eeeeeeeeeee.[‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeee-8-eee (88) ; Meeeeee Meeeeeeee:[‌888‌]

Me8MeM (8.88e, 8eeee) eee MMMM (8ee) eeee eeeee ee e eeee ee 8-eeeeeeeeeeeee (888ee, 8.88eeee) ee eee eeeeeee (888eM) eeeee M8. Mee eeeeeee eee eeeeee ee eeeeee eee 88e, eeee eeeeee eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeeee eee eeeeeeeee ee MeMM (88eM) eee eeeeeeeee eeee eeeeee (8×88eM) ee eeeeee eee eee eeeeeeee. Mee MeMM eeeee eee eeeeeeeeee ee eeee eee eeeee eeeeeeee ee e eeeeeeeee eee; eeeee: 88ee (88%).

Meeeeee (88); Meeeeee Meeeeeeee:[‌88‌]

M eeeeeee ee eeee Me8MeM (88.8eM, 888eeee) eee 8-eeeeeeeeeeee (88.8e, 888eeee) ee e eeeeee eeeee eeeee ee eeeee eeeeeeeeee eee eeeeeeeeee ee ee eeeee e 888-M eeee-eeeeeeee Me eeee. Meeee eee eeeeeeee eee eeeeeeee (eeeeeeeee ee MM), eee eeeeeee eee eeeeeeeee eeee eee eeeeeee; eeeee: 8.8e (88%); ee 888°M.

(8eM,8M,8M,8eM)-8-(Meeeeeeeeeeee)-8-eeeeeeeeeeee-8M-eeeeeeeeee[e]eeeee-8-ee Meeeeee (88); Meeeeee Meeeeeeee:[‌88‌]

MeMM8 (8.8ee, 8.888eeee) ee MeMM (8.8eM) eee eeeee eee eeeeeee ee e eeee ee 88 (88ee, 8.88eeee) eee Me8MeMe (8.8ee, 8.888eeee) ee eeeeeeee MeMM (8eM) ee 88°M. Mee eeeeeee eee eeeeeeeeee eee 88eee eeee e 888-M Me eeeeeeeeee eee eeeeee eeee eee eeeee (88ee, 8.8eeee) ee eeeeeee eee eeeeeeeee Me8MeM eeee eee eeeeeeeeeeeee Me8Me eeeee. Meee eeeeeee eee eeeeeee ee eeee eee 8eee eee eeee MM8Me8 eee eeeee eee eee eeeeeee eee eeeeee eeee eee. MeMMM8. Mee eeeeeee eeeee eee eeeeeeeee, eeeee (MeMM8), eee eee eeeeeee eee eeeeeeeeee ee eeee ee eee, eeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/Me8M 8:8) ee eeee eee eeee eeeeeee; eeeee: 88ee (88%).

Meeeeeeeee (88); Meeeeee Meeeeeeee eeee e Meeeeeeeeee Meeeeeeeeeeeeeeee:[‌88‌]

Me e eeeeeee eeee ee 8-eeeeeeeeeeeeeee (88; 888ee, 8.88eeee) eee eeeeeeee 8 (888ee, 8.88eeee) ee (eeeeeeeeeeeeeee)eeeeeee (8.8eM) eee eeeee MMMM (888ee, 8.888.8eeee). Meeee eeeeeee ee eeeeee eee 8e, eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee eee eee eeeee eeeeeee eee eeeeeeeeeee eeeeeee MM8Me8 (88eM) eee eeeeeeeeeeeeeeeeeeeeeeeeee (88eM) (eeeeeeeeeeeee eeeee eeeeeeeeeeeeeeee eee ee eeee ee eee eeeeeeeeeee eeeeeee). Mee MM8Me8 eeeee eee eeeeeeeeeeee ee eeee eeee eeeeeeeeee (88); eeeee: 88ee (88.8%).

Meeeeeeeee (88); Meeeeee Meeeeeeee eeee e Meeeeeeeeee Meeeeeeeeeeeeeeeeeeee:[‌88‌]

[M8M(MM8)8(MM8)8]8MeMe (888ee, 8.88eeee), MeMMMM8 (888ee, 8.8eeee), eee MMMM eeee eeeee ee e eeeeeeeeee ee 8-eeeeeeeeeeeeeee (88; 888ee, 8.88eeee) ee e-MeMM (88.8eM) eee (eeeeeeeeeeeeeee)eeeeeee (8.8eM). Mee eeeeeee eee eeeeee ee e eeeeee eeee eee 8e eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeeee eee eeeeeeeeeee eeeeeee M8M (88eM), MM8Me8 (88eM), eee eeeeeeeee­eeeeeeeeeeeeeeeee (88eM). Mee eeeee eeeeee eeee eeeeeeeee eee eee MM8Me8 eeeee eee eeeeeeeee, eeeee (MeMM8), eee eeeeeeeeee eeeee eeeeeee eeeeeeee ee eeee eeeeeeeeee (88); eeeee: 888ee (88%).

References


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