s. W I N S T E I N AND LEONG O O D h L 4 N
4 :1 Ti S
Vol. 7G
[CONTRIBUTION FROM THE DEPARTMENT O F CHEMISTRY O F THE UNIVERSITY OF CALIFORNIA AT L O S ANGELES]
Neighboring Groups in Addition. 11. Hydroxyl and Acetoxy Groups in Allyl Derivatives's' BY
s. WINSTEINA N D LEONGOODMAN RECEIVED FEBRUARY 24, 1954
Participation of neighboring groups in the process of addition of an electrophilic reagent to the carbon-carbon double bond is analogous t o similar participation in substitution. Just as in substitution, neighboring group intervention in the addition process competes with participation of solvent or added solutes. Groups with the largest driving forces in substitution can be expected to compete the best for involvement in addition reactions. W r n t i n g studies of halogen addition to allyl alcohol and allyl acetate show that no appreciable participation of the primarv hydroxyl and acetoxy groups occurs in the respective addition reactions. Under the conditions which are sliowti to pi'rmit survival of the expected epihalohydrins or orthoesters, no products from participation have been obtaiiird. These observations help t o delimit the scope of the contemplated phenomenon of participation of groups in additioii reactions.
Participation of a neighboring group G in nucleophilic displacement processes (I) is a general phen o m e n ~ n . ~G, ~may be a functional group (e.g., Br, OAc, etc.), a carbon substituent (e.g., R, aryl) or G N
\
G
G
.I. c
FZ I\ (4-.-+ \c /
I
\
c----c -(IF % \
I
\
I
I
E
G
4
,'+
C/3-Caru--+ // \y -y-
c'---c
//
'\
\\
hydrogen. This phenomenon may control stereochemistry and rate of reaction, the driving forces due to this kind of participation often being of an important order of magnitude. In the above phenomenon, the neighboring group G, with its associated electron cloud, assists in the toleration of electron-deficiency created by ionization of Y (J). It is obvious that similar participation by neighboring groups should be induced by other means of producing electron-deficiency, for example, attack of an electrophilic agent E 2 on an olefinic linkage. Without attempting here to exhaust the possible mechanistic variations, we can illustrate mechanisms foy the intervention of neighboring groups in processes of addition to multiple carbon-carbon linkages with those involving formation from I1 of 111, an olefin-E2 complex, which gives the G-bridged structure V either directly or by way of the E-bridged structure4 IV. Examples of I V are bromonium ions in bromium addition5 or the mercurinium ions in mercurations of olefins. S. Winstein, I,, Goodman and R . Boschan, T H r s J O U R N A L , 72, 2311 (1950). (2) Some of t h e material of this paper was presented in s u m m a r y : ( a ) before t h e Organic Division of t h e American Chemical Society a t St. Louis, September, 1948; (b) i n Abstracts of Eleventh S a t i o n a l Organic Symposium, 1949, page 6 5 . ( 3 ) S. Winstein, Bull. soc. chim., 151 18, 55C (1951). (4) There are classical analogs of t h e process I V -+ V , for example t h e
)LLc-c
