A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a "Crossed-Chain" Variant of in/out Stereoisomers.
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
Reactions of (O=)PH(OCH2 CH3 )2 and BrMg(CH2 )m CH=CH2 (4.9-3.2equiv; m=4 (a), 5 (b), 6 (c)) give the dialkylphosphine oxides (O=)PH[(CH2 )m CH=CH2 ]2 (2a-c; 77-81% after workup), which are treated with NaH and then ,-dibromides Br(CH2 )n Br (0.49-0.32equiv; n=8 (a'), 10 (b'), 12 (c'), 14 (d')) to yield the bis(trialkylphosphine oxides) [H2 C=CH(CH2 )m ]2 P(=O)(CH2 )n (O=)P[(CH2 )m CH=CH2 ]2 (3ab', 3bc', 3cd', 3ca'; 79-84%). Reactions of 3bc' and 3ca' with Grubbs' first-generation catalyst and then H2 /PtO2 afford the dibridgehead diphosphine dioxides (4bc', 4ca'; 14-19%, n'=2m+2); 31 PNMR spectra show two stereoisomeric species (ca. 70:30). Crystal structures of two isomers of the latter are obtained, out,out-4ca' and a conformer of in,out-4ca' that features crossed chains, such that the (O=)P vectors appear out,out. Whereas 4bc' resists crystallization, a byproduct derived from an alternative metathesis mode, (CH2 )12 P(=O)(CH2 )12 (O=)P(CH2 )12 , as well as 3ab' and 3bc', are structurally characterized. The efficiencies of other routes to dibridgehead diphosphorus compounds are compared.
