http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Selectivity in the amination of allylic alcohols via intramolecular amidomercuration
Intramolecular amidomercuration reactions of N-acylaminomethyl ether derivatives of α-substituted allylic alcohols were examined. High stereoselectivity was observed when ethers derived from 4-methyl-1-penten-3-ol and 1-phenyl-2-propen-1-ol were cyclized using mercuric acetate as the electrophile. The cyclization of an ether derived from 3-buten-2-ol gave trans- and cis-4,5-dimethyloxazolidines with moderate stereoselectivity (3:1) under identical conditions. Regioselectivity in intramolecular mercuric-ion initiated cyclizations of N-acylaminomethyl ether derivatives of α,γ-disubstituted allylic alcohols were examined. Mixtures of N-acyl-4,5-dialkyloxazolidine products (125) and N-acyl-4,6-dialkyl-1,3-tetrahydrooxazine products (126) were obtained when either carbamate derived from E-3-penten-2-ol (115E) or Z-3-penten-2-ol (115Z) was treated with mercuric trifluoroacetate. The geometry of the disubstituted double bond (E or Z) was found to affect the regioselectivity. When 115E was cyclized, 1,3-tetrahydrooxazine products (trans-126 and cis-126) predominated over the oxazolidine products in a ratio of 2:1. However, in the cyclization of 115Z, oxazolidine products (trans-125 and cis-125) predominated over the 1,3-tetrahydrooxazine products (2:1). Considering stereochemistry, trans-125 was the major oxazolidine stereoisomer when either 115Z or 115E was cyclized and reduced. However, the stereochemistry of the 1,3-tetrahydrooxazine products depended on the reaction conditions. The kinetically controlled product (cis-126:trans-126 ratio of 17:1), obtained by cyclization of 115E with mercuric trifluoroacetate for 15 min, equilibrated to a 1:29 (cis-126:trans-126) ratio after 11 days of reaction. Likewise, the kinetically controlled product (cis-126:trans-126 ratio of 2:1), obtained by the cyclization of 115Z with mercuric trifluoroacetate for 19 min, equilibrated to a 1:20 diastereomeric ratio of 1,3-tetrahydrooxazines (cis-126:trans-126) after 40 hours of reaction. High regioselectivity was observed when the N-acylaminomethyl ether derived from either E-4-benzyloxy-2-buten-1-ol or Z-4-benzyloxy-2-buten-1-ol was cyclized using mercuric nitrate to give an oxazolidine as the only product. High stereoselectivity was observed when the N-acylaminomethyl ether derived from allyl alcohol was treated with mercuric trifluoroacetate to give N-benzyloxycarbonyl-2-(trichloromethyl)-4-methyloxazolidine (164) as a single product...