The Origins of the Benzotriazole Project, Its Versatility Illustrated by a New -C=CHCH+OEt Synthon, and Novel Syntheses of α,β-Unsaturated Aldehydes and Ketones, Furans, Pyrroles and Allyl Ethers
Various 2(5H)-furanone and furan derivatives were synthesized from 3-(phenylthio)propenal by a one-pot process via carbonyl addition of a range of organometallic reagents and subsequent sulfide-directed α-lithiatin followed by electrophilic trapping. This methodology was successfuly applied to the syntheses of quercus lactone and 2, 5-diarylfuran natural products.
A new synthesis of 1-phenylthio- and 1-alkylamino-4-nitrobuta-1,3-dienes
作者:Noboru Ono、Koji Matsumoto、Takuji Ogawa、Hiroyuki Tani、Hidemitsu Uno
DOI:10.1039/p19960001905
日期:——
A new synthesis of push-pull dienes such as 4-nitro-1-phenylthiopenta-1,3-diene 4 and 1-dialkylamino-4-nitropenta-1,3-diene 5, is described. The X-ray crystal analysis shows that 4-nitro-1-(pyrrolidin-1-yl)penta-1,3-diene 5a is essentially planar in an E,E-configuration with r(C–C)= 1.42(1)Å and r(CC)= 1.35(1) and 1.371(9)Å. Compounds 5 showed a large solvatochromic effects similar to that of merocyanine dyes. Molecule 5a exhibits second harmonic generation (SHG) activity whose efficiency is 2.5 times that of urea (determined by a powder method at 1064 nm). For 5a, the molecular nonlinearity µβ is estimated to be 1200 × 10–48 esu which is calculated from the Pockel coefficient (r33) determined by electrooptic measurements of poled polymers of 5a in poly(methyl methacrylate) at 1300 nm. This value is relatively large for such small conjugated molecules, where donors and acceptors are bridged by only 4π electron systems.
diffraction. The thiomethyl groups in 6a–6c are close to be coplanar to the flat ringsystem, the strain due to the interaction of methyl with the hydrogen at C1 is released by shifting of the sulfur atom away from carbon C1 and opening of the angle C8–S-methyl. This coplanarity of the thiomethyl group with ringsystem agrees with the preference of the syn conformation of methyl vinyl thioether. In
Synthesis of a 1α,25-dihydroxyvitamin D<sub>3</sub>A ring model by an acyl radical cyclization
作者:Duncan Batty、David Crich、Simon M. Fortt
DOI:10.1039/c39890001366
日期:——
The synthesis of (±)-(2), an A ringmodel for 1α,25-dihydroxyvitamin D3 has been achieved in 7 steps from ethyl acetoacetate, with an acylradicalcyclization as the key ring forming step.